System and method for providing residual stress test structures

A system configured to determine residual stress of a deposited film, comprising:

• one or more test units, each test unit comprising a reflective membrane that comprises a portion of the deposited film, wherein the membrane is configured as a parallelogram with at least a portion of each side attached to a substrate, wherein the membrane is configured to deform based on the residual stress of the film and modulate light indicative of the amount of membrane deformation;
• an imaging system positionable to receive modulated light reflecting from the one or more test units and configured to produce image data associated with the received light;
• and
• a computer in communication with the imaging system, the computer configured to process the image data and generate information relating to the residual stress in the film.

A system for measuring residual stress in a deposited film, comprising:

• a test unit comprising
• a reflective membrane attached to the substrate, the test unit configured to modulate light using an interferometric cavity formed between the membrane and the substrate and wherein the membrane comprises a portion of the deposited film;
• an electrode disposed such that at least a portion of the interferometric cavity is between the electrode and the membrane;
• and
• a power source configured to apply a voltage between the membrane and the electrode,
• wherein the test unit is configured such that the membrane moves at a frequency in response to the applied voltage, and wherein the modulated light is indicative of when the beam is moving at a resonant frequency, the resonant frequency being based on the residual stress of the deposited film.

A method of measuring residual stress in a deposited film, comprising:

• moving a membrane attached to the substrate at a resonant frequency wherein the membrane comprises a portion of the deposited film;
• modulating light interferometrically based on the movement of the membrane;
• detecting the modulated light;
• and
• determining the residual stress in the deposited film based on the detected modulated light.

A system for measuring residual stress in a deposited film, comprising:

• means for moving a membrane attached to the substrate at a resonant frequency;
• means for modulating light interferometrically based on the movement of the membrane;
• means for detecting the modulated light;
• and
• means for determining the residual stress in the film based on the detected modulated light.

A method of manufacturing a test unit to indicate the residual stress in a film, the method comprising:

• disposing a reflective membrane on a substrate such that an interferometric cavity is formed between a portion of the membrane and a portion of the substrate, wherein the membrane is connected to the substrate on two opposite and parallel sides, wherein the membrane comprises a portion of the film, and wherein the membrane configured to deform based on the residual stress of the film and modulate light indicative of the amount of deformation;
• disposing an electrode such that the interferometric cavity is between the membrane and the electrode;
• and
• connecting a voltage source to the membrane and the electrode, the voltage source configured to provide voltage across the membrane and electrode such that the membrane moves at a resonant frequency.

A display device, comprising:

• a substrate;
• one or more one bi-stable display elements disposed on the substrate wherein each the one or more bi-stable display elements comprise a moveable membrane which comprises a portion of a film;
• and
• one or more test units, each test unit comprising a membrane defining a portion of an interferometric cavity, wherein the membrane comprises a portion of the film, wherein the one or more test units are configured to modulate light such that the modulated light is indicative of the residual stress of the film.

A method of determining residual stress of a film layer incorporated in a display, comprising:

• interferometrically modulating light, wherein the modulated light is indicative of the residual stress in the film layer;
• detecting the modulated light;
• generating image data associated with the detected modulated light;
• and
• determining residual stress of the film layer of the display based on the image data.

A system for determining residual stress in film incorporated in a display, comprising:

• means for interferometrically modulating light at one or more test units disposed near a display, wherein the modulated light is indicative of the residual stress in the film;
• means for detecting the modulated light;
• means for generating image data associated with the detected modulated light;
• and
• means for determining residual stress in the film based on the image data.