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US 6,567,715 B1Granted
Method and system for automated on-chip material and structural certification of MEMS devices
AssigneeSandia Corporation
InventorsMichael B. Sinclair, Maarten P. DeBoer, Norman F. Smith, Brian D. Jensen, Samuel L. Miller
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Abstract
A new approach toward MEMS quality control and materials characterization is provided by a combined test structure measurement and mechanical response modeling approach. Simple test structures are cofabricated with the MEMS devices being produced. These test structures are designed to isolate certain types of physical response, so that measurement of their behavior under applied stress can be easily interpreted as quality control and material properties information.
Claims36
A method for quality control of MEMS fabrication processes, comprising the steps of:
- a) fabricating MEMS structures on a substrate;
- b) co-fabricating at least one IMaP test structure on said substrate, said at least one IMaP test structure comprising at least one anchor to said substrate, at least one compliant member functionally attached to said anchor, at least one electrostatic actuator so configured as to apply mechanical stress to said at least one compliant member, at least one diagnostic surface whose shape is determined by the response of said at least one compliant member to said mechanical stress, and contact sites whereby each such electrostatic actuator can be actuated by a voltage applied to said contact sites;
- c) releasing the at least one IMaP test structure from the substrate;
- d) evaluating the substrate by automated process steps comprising:
- α) making effective electrical contact between an external voltage source and said contact sites;
- β) actuating at least one of the at least one IMaP test structures by applying prescribed test voltages to said electrostatic actuators via said contact sites;
- γ) measuring the displacement of the diagnostic surfaces of the actuated IMaP test structures;
- δ) comparing said displacement with corresponding standards for a high-quality fabrication process;
- and,
- ε) rejecting said substrate if said comparison reveals process flaws outside of pre-established tolerances.
7 more elements
A MEMS fabrication quality control apparatus, comprising:
- a) a mount capable of holding at least one process wafer without inducing unacceptably large values of mounting stress in the at least one process wafer, all of said at least one process wafer having at least one IMaP test structure fabricated thereon, said at least one IMaP test structure comprising at least one anchor to said process wafer, at least one compliant member functionally attached to said anchor, at least one electrostatic actuator so configured as to apply mechanical stress to said at least one compliant member, at least one diagnostic surface whose shape is determined by the response of said at least one compliant member to said mechanical stress, and contact sites whereby each such electrostatic actuator can be actuated by a voltage applied to said contact sites;
- b) voltage probes capable of making electrical contact to said contact sites;
- c) a voltage source functionally connected to said voltage probes, and which applies voltages as controlled by voltage control data;
- d) an imaging optical interferometer comprising a camera which captures an optical interferometric image, converts said image into image data suitable for automated computer analysis, and transmits said image data to an apparatus controller;
- e) a positioner which adjusts the relative position and orientation of the voltage probes, the imaging optical interferometer, and the mount in response to position control data;
- f) said apparatus controller, comprising:
- 1) a control computer comprising a central processing unit, a voltage control data source, a position control data source, an image data input receptor, and reporting means to report the results of the quality control analysis;
- 2) control software which directs the MEMS fabrication quality control apparatus to carry out steps including:
- a) positioning the voltage probes, the imaging optical interferometer, and the mount so that the optical interferometric image provided by the imaging optical interferometer includes the image of an IMaP test structure, including its diagnostic surfaces, and also so that the voltage probes make electrical contact with the contact sites connected to said imaged IMaP test structure;
- b) generating voltage control data so that voltages programmed to activate the imaged IMaP test structure are applied to the voltage probes;
- c) commanding the control computer to accept image data from said camera;
- d) analyzing said image data to determine the shape of the diagnostic surfaces of the imaged IMaP test structure;
- and,
- e) evaluating the level of process quality by analyzing the diagnostic surface shapes for the imaged IMaP test structure.
11 more elements
Dependencies are inferred from the claim text.