WO2010121846A1 - Method and inspection system for testing of micro fabricated structures - Google Patents

Method and inspection system for testing of micro fabricated structures Download PDF

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Publication number
WO2010121846A1
WO2010121846A1 PCT/EP2010/052041 EP2010052041W WO2010121846A1 WO 2010121846 A1 WO2010121846 A1 WO 2010121846A1 EP 2010052041 W EP2010052041 W EP 2010052041W WO 2010121846 A1 WO2010121846 A1 WO 2010121846A1
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Prior art keywords
actuator
mems
wafer
structures
microscope
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PCT/EP2010/052041
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French (fr)
Inventor
Felix Beyeler
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Femtotools Gmbh
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Publication of WO2010121846A1 publication Critical patent/WO2010121846A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
    • B81C99/00—Subject matter not provided for in other groups of this subclass
    • B81C99/0035—Testing
    • B81C99/005—Test apparatus
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/32—Investigating strength properties of solid materials by application of mechanical stress by applying repeated or pulsating forces
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/0095—Semiconductive materials
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/003—Generation of the force
    • G01N2203/005—Electromagnetic means
    • G01N2203/0051—Piezoelectric means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/02—Details not specific for a particular testing method
    • G01N2203/026—Specifications of the specimen
    • G01N2203/0286—Miniature specimen; Testing on microregions of a specimen

Definitions

  • the invention relates to a method and inspection system for testing of micro fabricated structures preambles of the independent claims.
  • MEMS Micro-ElectroMechanical Systems
  • MEMS structures are easily damaged due to their delicate buildup and use of brittle materials such as silicon. It is important to identify defective structures before packaging them, since packaging often times accounts for a large portion of the production costs.
  • the following typical questions must be answered during quality control to find out if the mechanical properties are acceptable for the next manufacturing step: Is the mechanical micro-structure released from the base substrate so it can move? Are the damaged elastic micro-structures? - Is the mass of the movable structures within the tolerances?
  • MEMS transducers have structures which are moving a high speeds and feature high resonance frequencies. Outside a vacuum environment these movements are highly damped due to the viscosity of air.
  • MEMS structures such as comb drives are dominated by squeeze film damping which results in high values for B and over- critically damped structures. This damping effect prevents large deflections.
  • the only way to reduce B without changing the MEMS design is to lower the ambient viscosity. This can be done by evacuating the air and do the testing in vacuum.
  • the damping coefficient B is proportional to the air pressure p.
  • Piezoelectricity is the ability of some materials to generate an electric potential in response to applied mechanical stress.
  • the piezoelectric effect is reversible in that materials exhibiting the direct piezoelectric effect also exhibit the converse piezoelectric effect (the production of stress and/or strain when an electric field is applied) .
  • lead zirconate titanate crystals will exhibit a maximum shape change of about 0.1% of the original dimension.
  • piezoelectric actuators can be used the mechanical excitation of MEMS structures on a chip or a whole wafer.
  • a compression/extension motion can be generated or a shear motion.
  • a single actuator is often built up by multiple actuators forming a piezoelectric actuator stack.
  • US 6,587,212 Bl [1] describes a wafer-level packaging and visual inspection by windows on the MEMS dies. This patent US 6,587,212 Bl [1] does not make use of piezoelectric actuation to vibrate the MEMS structures.
  • US 7,065,239 B2 [2] describes a method for inspecting repetitive structures on a wafer.
  • This patent US 7,065,239 B2 [2] does not make use of piezoelectric actuation to vibrate the MEMS structures. This method is not suitable for testing inertial MEMS sensors, force sensors and resonators.
  • US 6,317,506 Bl [3] describes a system for visually measure the motion of MEMS.
  • This patent US 6,317,506 Bl [3] does not make use of piezoelectric actuation to vibrate the MEMS structures.
  • US 7,248,354 B2 [4] describes a system for MEMS inspection. An illumination beam is used to illuminate a spot on the MEMS structure and detect deflections. This patent US 7,248,354 B2 [4] does not make use of piezoelectric actuation to vibrate the MEMS structures.
  • the PMA-400 Planar Motion Analyzer according to [7] is designed for in-plane microstructure vibration and motion analysis. Piezoelectric actuation is used to excite the micro- structures. The main difference is that a strobe system is used for illumination and that deflections are measured. The system is not designed to analyze blurriness for the detection of defective micro fabricated structures.
  • the Inspection system allows a testing of mechanical properties on both single device level and on wafer level.
  • the inspection system includes a piezoelectric actuator for vibra- ting a wafer or a single microstructure and a microscope for monitoring the vibrations of the waver or the MEMS structures.
  • the wafer or microstructure is mounted on the piezoelectric actuator. The vibrations of the wafer/microstructures are visually observed while exciting it with the piezoelectric actuator. By finding the resonance frequencies, the mechanical properties of the micro fabricated structures are obtained.
  • Fig 1 Visual inspection system
  • Fig 2 Visual inspection system using a stage for positioning of the wafer and multiple cameras for parallel inspection;
  • Fig 3 Visual inspection system using a stage for positioning of the wafer and multiple cameras for parallel inspection
  • Fig 4 Side view of the micro fabricated structure mounted on the piezoelectric actuator.
  • FIG. 1 illustrates the basic buildup of the inspection system.
  • a vacuum chamber 1 can be evacuated by a vacuum pump, not shown in Fig. 1.
  • a feed-trough 2 allows electrical wiring for components inside the chamber.
  • the top cover 3 is made of a transparent material. Inside the vacuum chamber 1 a piezoelectric actuator 4 is attached. More than one piezoelectric actuator 4 may be used also.
  • the micro fabricated structures which can be a single MEMS structure or a whole wafer 5, are mounted on the piezoelectric actuator 4.
  • a microscope 6 or microscope camera 6 is placed above the chamber 1 so the micro fabricated structures can be seen.
  • the top cover 3 or the vacuum chamber 1 includes a connector for the vacuum tube 7.
  • a voltage source (frequency generator) is used to vibrate the piezoelectric actuator 4.
  • the actuation signal can be sinusoidal or any other signal.
  • the amplitude of the vibrations of the piezoelectric actuator 4 are small (sub-micrometer) and do not need to be seen by the microscope or a microscope camera 6.
  • the elastic MEMS microstructure 13 is damaged (broken flexures) the tolerance.
  • a defect in the microstructure prevents the deflection of the microstructure 12.
  • This method can be applied for multiple types of MEMS transducers. It is especially suitable for devices using capa- citive comb drive electrodes (accelerometers, gyroscopes, level sensors, force sensors, mechanical resonators and micro- grippers) .
  • the proposed method is a non-contact, non-destructive method.
  • a positioning system 8 can be used as shown in Figure 2.
  • the positioning system 8 consists of a single-axis positioner or a multi-axis positioner.
  • the positioning system 8 may be manual or motor driven (DC-motors, stepper motors or piezo-actuators) . Either the vacuum chamber 1 or the microscope/ camera 6 may be moved.
  • the positioning system 8 enables the fast and automated inspection of a large number of devices on a wafer.
  • the microscope 6 can be equipped with a digital camera or a microscope camera. In combination with state-of-the art vision inspection software, the system can then be used for fully automated inspection.
  • a pressure sensor may be integrated inside the vacuum chamber 1. Knowing the pressure helps finding a suitable pump- down time and also helps calculating the damping coefficients of the MEMS structures.
  • the working distance of the microscope lens is usually very small.
  • the microscope (s) or microscope camera (s) may be placed inside the vacuum chamber.
  • the vacuum chamber may not be required.
  • Inertial MEMS sensors, gyroscopes, resonators, level sensors and force sensors often feature stiffness variations. To overcome stiffness variations and enable high accuracy measurements, the sensors must be calibrated. By measuring the resonance of the MEMS structure at a certain air pressure, the stiffness can be derived.
  • more than one microscope cameras can be used. Multiple microscopes (10) are placed next to each other at a defined distance, observing MEMS structures in parallel. The total time required for inspecting the structures is divided by the number of microscopes. A single microscope may be used for the inspection of multiple MEMS structures within the field of view of the camera .
  • a multi-axis piezoactuator 4 may be used to vibrate the structures in different directions.
  • a multi-axis piezoactuator 4 can be built by mounting two shear-type actuators on top of each other. This enables the testing of multi-axis sensors. Also, the direction of the vibration can be controlled.
  • FIG. 1 shows a basic setup for inspecting encapsulated structures.
  • a light source 10 is used to shine infrared light through the wafer which is seen by the infrared camera 6 on the opposite side of the wafer.
  • the piezoelectric actuator 4 is moved to the side of the wafer.
  • the vacuum chamber 1 is not required and not useful when working with sealed structures.
  • Non-movable MEMS structure / Anchor area 15 Insulating layer / Silicon dioxide

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  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Physics & Mathematics (AREA)
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  • Engineering & Computer Science (AREA)
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Abstract

The invention includes a system for the visual inspection of micro fabricated structures (12, 13, 14) such as accelerometers, gyroscopes, level sensors, force sensors, mechanical resonators or microgrippers. The system allows testing of mechanical properties on both single device level and on wafer level. The system includes a piezoelectric actuator (4) for vibrating a wafer (5) or a single microstructure and a microscope (6). The wafer (5) or microstructure is mounted on the piezoelectric actuator (4). The wafer/microstructures (12, 13) are visually observed while exciting it with the piezoelectric actuator (4). By finding the resonance frequencies, the mechanical properties of the micro fabricated structures (12, 13) are obtained. This method is used for detecting defects in the microstructure.

Description

Method and inspection system for testing of micro fabricated structures
[0001] The invention relates to a method and inspection system for testing of micro fabricated structures preambles of the independent claims.
Background
1 Inspection of micro fabricated structures
[0002] Micro-ElectroMechanical Systems MEMS often times suffer from poor relative geometrical tolerances. Also, MEMS structures are easily damaged due to their delicate buildup and use of brittle materials such as silicon. It is important to identify defective structures before packaging them, since packaging often times accounts for a large portion of the production costs. The following typical questions must be answered during quality control to find out if the mechanical properties are acceptable for the next manufacturing step: Is the mechanical micro-structure released from the base substrate so it can move? Are the damaged elastic micro-structures? - Is the mass of the movable structures within the tolerances?
Is the stiffness of the elastic structure within the tolerances?
Is there a defect in the structure which prevents a movement of the micro-structures?
[0003] Multiple ways for inspecting MEMS devices on a wafer exist. One of the most popular is visual inspection. Regular visual inspection cannot answer all the questions. It is not possible to see whether the device is fully released from the substrate. Also, the spatial resolution of the visual system is limited and does not directly allow measurements of the mechanical stiffness of the structure. The method presented in this work is based on detecting the resonance frequencies of the microstructure by vibrating the MEMS structure or the whole wafer. Air damping is reduced by performing the inspection in vacuum which enables to see the large deflections of the micro fabricated structures at resonance.
2 Excitation of micro fabricated structures
[0004] Most MEMS transducers have structures which are moving a high speeds and feature high resonance frequencies. Outside a vacuum environment these movements are highly damped due to the viscosity of air. An elastic, movable MEMS structure can be modeled by the equation of motion mx = -F -BxF -kxF , ( I ) [0005] where m is the mass of the structure, xF the deflection of the structure, F the externally applied force, B the damping coefficient and k the spring constant of the elastic structure. MEMS structures such as comb drives are dominated by squeeze film damping which results in high values for B and over- critically damped structures. This damping effect prevents large deflections. The only way to reduce B without changing the MEMS design is to lower the ambient viscosity. This can be done by evacuating the air and do the testing in vacuum. The damping coefficient B is proportional to the air pressure p.
B ~ p (II) .
[0006] In vacuum, the damping can almost be neglected. The resonance frequency Cϋr of the microstructure is then calculated by
ωr = I— (in) . V m [0007] A defect in the micro fabricated structure will either change k, m or both k and m and therefore result in a different resonance frequency Cϋr .
3 Piezoelectric actuators
[0008] Piezoelectricity is the ability of some materials to generate an electric potential in response to applied mechanical stress. The piezoelectric effect is reversible in that materials exhibiting the direct piezoelectric effect also exhibit the converse piezoelectric effect (the production of stress and/or strain when an electric field is applied) . For example, lead zirconate titanate crystals will exhibit a maximum shape change of about 0.1% of the original dimension.
[0009] Due to the high actuation speed and high natural fre- quencies, piezoelectric actuators can be used the mechanical excitation of MEMS structures on a chip or a whole wafer.
[0010] Depending on the orientation of the piezoelectric crystal, a compression/extension motion can be generated or a shear motion. For increasing the deflection of the piezo- electric actuator, a single actuator is often built up by multiple actuators forming a piezoelectric actuator stack.
4 State of the art
[0011] US 6,587,212 Bl [1] describes a wafer-level packaging and visual inspection by windows on the MEMS dies. This patent US 6,587,212 Bl [1] does not make use of piezoelectric actuation to vibrate the MEMS structures.
[0012] US 7,065,239 B2 [2] describes a method for inspecting repetitive structures on a wafer. This patent US 7,065,239 B2 [2] does not make use of piezoelectric actuation to vibrate the MEMS structures. This method is not suitable for testing inertial MEMS sensors, force sensors and resonators.
[0013] US 6,317,506 Bl [3] describes a system for visually measure the motion of MEMS. This patent US 6,317,506 Bl [3] does not make use of piezoelectric actuation to vibrate the MEMS structures.
[0014] US 7,248,354 B2 [4] describes a system for MEMS inspection. An illumination beam is used to illuminate a spot on the MEMS structure and detect deflections. This patent US 7,248,354 B2 [4] does not make use of piezoelectric actuation to vibrate the MEMS structures.
[0015] In US 7,466,018 B2 [5] a piezoelectric actuation is used to excite the microstructures . Laser Doppler deflection measurement is used rather than a vision system such as a microscope or a microscope camera. [0016] In US 6,587,212 Bl [6] an amplitude and phase of an electro-acoustic device are measured by interferometry . This patent US 6,587,212 Bl [6] does not make use of piezoelectric actuation to vibrate the MEMS structures.
[0017] The PMA-400 Planar Motion Analyzer according to [7] is designed for in-plane microstructure vibration and motion analysis. Piezoelectric actuation is used to excite the micro- structures. The main difference is that a strobe system is used for illumination and that deflections are measured. The system is not designed to analyze blurriness for the detection of defective micro fabricated structures.
5 Summary of the invention
[0018] It is therefore a task of the present invention, to provide a inspection system and a method, which allow an ana- lyzing of micro fabricated structures regarding mechanical defects. The method and the system should be based on simple but reliable principles for analyzing micro fabricated structures MEMS or wafers.
[0019] This task is solved according to the features given in the independent claims. Further embodiments result from the depending claims.
[0020] The Inspection system allows a testing of mechanical properties on both single device level and on wafer level. The inspection system includes a piezoelectric actuator for vibra- ting a wafer or a single microstructure and a microscope for monitoring the vibrations of the waver or the MEMS structures. The wafer or microstructure is mounted on the piezoelectric actuator. The vibrations of the wafer/microstructures are visually observed while exciting it with the piezoelectric actuator. By finding the resonance frequencies, the mechanical properties of the micro fabricated structures are obtained. [0021] The invention will now be described with reference to the drawing cited below wherein is shown:
[0022] Fig 1: Visual inspection system;
[0023] Fig 2: Visual inspection system using a stage for positioning of the wafer and multiple cameras for parallel inspection;
[0024] Fig 3: Visual inspection system using a stage for positioning of the wafer and multiple cameras for parallel inspection;
[0025] Fig 4: Side view of the micro fabricated structure mounted on the piezoelectric actuator.
[0026] Figure 1 illustrates the basic buildup of the inspection system. A vacuum chamber 1 can be evacuated by a vacuum pump, not shown in Fig. 1. A feed-trough 2 allows electrical wiring for components inside the chamber. The top cover 3 is made of a transparent material. Inside the vacuum chamber 1 a piezoelectric actuator 4 is attached. More than one piezoelectric actuator 4 may be used also. The micro fabricated structures, which can be a single MEMS structure or a whole wafer 5, are mounted on the piezoelectric actuator 4. A microscope 6 or microscope camera 6 is placed above the chamber 1 so the micro fabricated structures can be seen. The top cover 3 or the vacuum chamber 1 includes a connector for the vacuum tube 7.
[0027] A voltage source (frequency generator) is used to vibrate the piezoelectric actuator 4. The actuation signal can be sinusoidal or any other signal. The amplitude of the vibrations of the piezoelectric actuator 4 are small (sub-micrometer) and do not need to be seen by the microscope or a microscope camera 6.
[0028] While monitoring vibrations of the MEMS structures 12 and 13, the frequency is changed. When exciting the structures 12, 13 at their resonance frequency frr large deflections of the MEMS structures 12, 13 can be observed. The vacuum environment reduces the damping which enables even larger deflections (several micrometers) . The monitoring can be made with means connected with a microscop camera such as a computer and appropriate software. In this software an edge diction algo- rithm or intensity distribution analysis of the microscope image is preferably implemented.
[0029] If no deflection can be observed at the natural frequency of the MEMS structure 12, one of the following problems exists with the MEMS structure 12 and 13: - The MEMS microstructure 12 is not released from the base substrate .
- The elastic MEMS microstructure 13 is damaged (broken flexures) the tolerance.
- A defect in the microstructure (wafer 5, insulating layer 15) prevents the deflection of the microstructure 12.
[0030] This method can be applied for multiple types of MEMS transducers. It is especially suitable for devices using capa- citive comb drive electrodes (accelerometers, gyroscopes, level sensors, force sensors, mechanical resonators and micro- grippers) . The proposed method is a non-contact, non-destructive method.
[0031] For the relative alignment of the microscopes field of view and the structure on the wafer (or MEMS chip) , a positioning system 8 can be used as shown in Figure 2.
[0032] The positioning system 8 consists of a single-axis positioner or a multi-axis positioner. The positioning system 8 may be manual or motor driven (DC-motors, stepper motors or piezo-actuators) . Either the vacuum chamber 1 or the microscope/ camera 6 may be moved. The positioning system 8 enables the fast and automated inspection of a large number of devices on a wafer.
[0033] The microscope 6 can be equipped with a digital camera or a microscope camera. In combination with state-of-the art vision inspection software, the system can then be used for fully automated inspection. [0034] A pressure sensor may be integrated inside the vacuum chamber 1. Knowing the pressure helps finding a suitable pump- down time and also helps calculating the damping coefficients of the MEMS structures.
[0035] When working with microscopes 6 featuring a high magnification factor, the working distance of the microscope lens is usually very small. In that case the microscope (s) or microscope camera (s) may be placed inside the vacuum chamber.
[0036] For devices featuring low damping, the vacuum chamber may not be required.
[0037] Inertial MEMS sensors, gyroscopes, resonators, level sensors and force sensors often feature stiffness variations. To overcome stiffness variations and enable high accuracy measurements, the sensors must be calibrated. By measuring the resonance of the MEMS structure at a certain air pressure, the stiffness can be derived.
[0038] For improving the speed of the inspection method, more than one microscope cameras can be used. Multiple microscopes (10) are placed next to each other at a defined distance, observing MEMS structures in parallel. The total time required for inspecting the structures is divided by the number of microscopes. A single microscope may be used for the inspection of multiple MEMS structures within the field of view of the camera .
[0039] A multi-axis piezoactuator 4 may be used to vibrate the structures in different directions. A multi-axis piezoactuator 4 can be built by mounting two shear-type actuators on top of each other. This enables the testing of multi-axis sensors. Also, the direction of the vibration can be controlled.
[0040] Many types of MEMS devices are encapsulated and hermetically sealed. One way to achieve sealing is to do a wafer- bonding process using a second wafer. This wafer is usually glass or silicon. If a glass wafer is used, the inspection method proposed in this document can be used without any design changes to the inspection system. If a silicon wafer is used the vibrating structures cannot be seen inside the wafer-stack. By using mid-infrared or far-infrared cameras this problem can be solved, since silicon is transparent for infrared light. Figure 3 shows a basic setup for inspecting encapsulated structures. A light source 10 is used to shine infrared light through the wafer which is seen by the infrared camera 6 on the opposite side of the wafer. The piezoelectric actuator 4 is moved to the side of the wafer. The vacuum chamber 1 is not required and not useful when working with sealed structures.
References
[1] US 7,466,018 B2 «MEMS device wafer-level package»
[2] US 7,065,239 B2 «Automated repetitive array microstructure defect inspection» [3] US 6,317,506 Bl «Measuring the characteristics of oscillating motion»
[4] US 7,248,354 B2 «Apparatus for inspection of a wafer»
[5] US 7,466,018 B2 «Method and apparatus for determining dynamic response of microstructure by using broad bandwidth ultrasonic transducer as baw hammer»
[6] US 6,587,212 Bl «Method and apparatus for studying vibrational modes of an electro-acoustic device»
[7] PMA-400 Planar Motion Analyzer by
Polytec GmbH DE 76333 Waldbronn; disclosed under h11p : //www . po1ytec . com .
List of used reference numerals
1 Vacuum chamber
2 Vacuum feed trough
3 Transparent cover plate, top cover 4 Piezoelectric actuator
5 Wafer or single MEMS die
6 Microscope or microscope camera
7 Vacuum connector
8 Positioning stage, positioning system 9 Adhesive tape
10 Infrared light source
12 Movable MEMS structure
13 Elastic MEMS structure
14 Non-movable MEMS structure / Anchor area 15 Insulating layer / Silicon dioxide

Claims

Claims
1. A method for analyzing micro fabricated structures (12, 13) - in the following called MEMS structures (12, 13) - which MEMS structures (12, 13,14 ) are mounted on a wafer (5), the method comprising the steps of fixing the wafer (5) on an actuator (4); vibrating the actuator (4) with a signal of a frequency generator, the vibration of the actuator causing a vibration of MEMS structures (12, 13); monitoring the vibration of MEMS structures (12, 13) by a microscope (6) via visualization.
2. The method according to claim 1, wherein the frequency of the signal is changed to a resonance frequency of a MEMS structure (12, 13) .
3. The method according to claim 1 or 2, wherein the step of monitoring is carried out with a microscope camera (6) .
4. The method according to one of the claims 1 to 3, wherein a piezo-electric actuator (4) is vibrated.
5. The method according to one of the claims 1 to 4, wherein the MEMS structures (12, 13) are placed in a vacuum environment (D •
6. The method according to one of the claims 1 to 5, wherein said actuator (4) is vibrated by an signal of sinusoidal, rectangular or triangular shape.
7. The method according to one of the claims 1 to 6, wherein the MEMS structure (12, 13) is mounted on the actuator (4) either by an adhesive glue (9) or adhesive tape (9) or a mechanical fixture or by electrostatic clamping.
8. The method according to one of the claims 1 to 7, wherein an infrared light source (10) is placed opposite to the microscope (6) in order visualize the vibration of the MEMS structure (12, 13) .
9. The method according to one of the claims 1 to 8, wherein the MEMS structures (12, 13) are surrounded by a vacuum chamber (1) featuring a detachable transparent cover made of either glass or a transparent polymer.
10. The method according to one of the claims 1 to 8, wherein said actuator (4) is a multi-axis actuator.
11. The method according to one of the claims 1 to 10, wherein said actuator (4) is mounted on a motorized or manual positioning stage (8) for inspecting multiple MEMS structures (12, 13) on a wafer (5) .
12. A visual inspection system for carrying out the method according to one of the claims 1 to 11, the visual inspection system comprising an actuator (4) connected with a frequency generator in order to vibrate the actuator (4); a mounted wafer (5) mounted on the actuator (4) the wafer (5) comprising a mounted MEMS structure (12, 13, 14); a microscope (6); characterized by means for monitoring with the microscope (6) a vibration of MEMS structures (12, 13), which vibrations are caused by the vibration of the actuator (4) .
13. Inspection system according to claim 12, wherein the vibration of MEMS structures (12, 13) are monitored with microscope camera (6)
14. Inspection system according to claim 12 or 13, wherein the actuator is a piezo-electric actuator (4).
15. Inspection system according to one of the claims 12 to 14, characterized by a vacuum environment (1) in which the MEMS structures (12, 13) are placed in.
16. Inspection system according to one of the claims 12 to 15, characterized by an infrared light source (10) is placed opposite to the microscope (6) in order visualize the deflection of the MEMS structures (12, 13) .
17. Inspection system according to one of the claims 12 to 16, characterized by a positioning stage (8) on which the actuator (4) is mounted.
PCT/EP2010/052041 2009-04-23 2010-02-18 Method and inspection system for testing of micro fabricated structures WO2010121846A1 (en)

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