Fabricating semiconductor devices such as logic and memory devices typically includes processing a substrate such as a semiconductor wafer using a large number of semiconductor fabrication processes to form various features and multiple levels of the semiconductor devices. Multiple semiconductor devices may be fabricated in an arrangement on a single semiconductor wafer and then separated into individual semiconductor devices.
Semiconductor devices may develop defects during the fabrication processes. As the demand for integrated circuits having ever-smaller device features continues to increase, the need for improved inspection systems of these ever-shrinking devices continues to grow. Compensating for misalignment of an illumination beam in these improved inspection systems becomes more and more critical, as even minute system jitter may directly impact capture rate of the ever-smaller devices.
System jitter may originate from multiple sources, resulting in a jitter frequency distribution ranging from 0.1 Hz to 100 Hz. One system jitter source is “air wiggle”, or turbulent air flow along the illumination beam path caused by purge air creating zones of pressure change and changing the refractive index of the air, which affects the pointing and translation components of a position of the illumination beam in a frequency range of 5 Hz to 100 Hz. Another system jitter source is the illumination light source, which will have intrinsic instabilities ranging in frequency from 0.5 to 10 Hz. A third source of system jitter is the mechanical vibration of inspection system components such as optic mounts and mechanical contacts, potentially excited by various external forces, which affect the pointing and translation components of the position of the illumination beam in a frequency range of 0.1 Hz to 100 Hz.
These system jitter sources are often too difficult to effectively remove from the inspection system, meaning the illumination beam will remain misaligned if not compensated for within the improved inspection systems.
As such, it would be desirable to provide a system and method for curing the shortcomings of previous approaches such as those identified above.