System for compensating for dark current in sensors
AssigneeASML Holdings N.V.
InventorWilly Sander
Life of this patent
Estimating the term…
Abstract
A method is used to perform dark current compensation in a sensor (e.g., a CCD or CMOS sensor). A first and second array of devices (e.g., pixels) in the sensor are used to determine a first dark current value. The first array of pixels in the sensor receives impinging light and generates optical energy values therefrom. The second array of pixels in the sensor are used to determine a second dark current value at substantially a same time as the generating of the optical energy values. The second array of devices being non-sensitive to the impinging light. The first and second dark current values are used to compensate the optical energy values.
Claims20
A system, comprising:
- a sensor having a first and second array of photosensitive devices, the sensor receiving a beam of radiation;
- a storage device coupled to the sensor that receives signals from the sensor based on the received beam of radiation;
- and
- a processing system coupled to the storage device, wherein
- the processing system determines a first dark current value based on signals accessed from the storage device corresponding to signals from the first and second array of photosensitive devices during a first time period;
- the processing system determines an optical energy value based on signals accessed from the storage device corresponding to signals from the first array of photosensitive devices during a second time period;
- the processing system determines a second dark current value based on signals accessed from the storage device corresponding to signals from the second array of photosensitive devices during the second time period;
- and
- the processing system adjusts the optical energy value based on the first and second dark current values.
A lithography system, comprising:
- an illumination system that conditions a beam of radiation;
- a patterning system that patterns the beam;
- a projection system that projects the patterned beam onto a target portion of a substrate supported on a stage;
- a sensor coupled to the stage adjacent the substrate, the sensor having a first and second array of photosensitive devices, the sensor receiving the patterned beams;
- a storage device coupled to the sensor that receives signals from the sensor based on the received patterned beam;
- and
- a processing system coupled to the storage device, wherein the processing system determines,
- a first dark current value based on signals accessed from the storage device corresponding to signals from the first and second array of photosensitive devices during a first time period,
- an optical energy value based on signals accessed from the storage device corresponding to signals from the first array of photosensitive devices during a second time period, and
- a second dark current value based on signals accessed from the storage device corresponding to signals from the second array of photosensitive devices during the second time period,
- wherein the processing system adjusts the optical energy value based on the first and second dark current values.
Dependencies are inferred from the claim text.