System and method for upstream purging in inspection systems

An inspection system comprising:

• an objective lens housing, wherein the objective lens housing is configured to house an objective lens;
• a motion sub-system configured to scan a sample along a scan direction, wherein the motion sub-system comprises:
• a linear stage to translate the sample along the scan direction, wherein one or more illumination optics direct one or more illumination beams to the sample as the sample is scanned by the linear stage;
• and
• a rotation spindle, wherein the linear stage is configured to linearly translate the rotation spindle during inspection;
• a purging sub-system configured to deliver a gas to the sample as the sample is scanned, wherein the purging sub-system comprises:
• a gas source configured to provide the gas;
• one or more flow valves;
• one or more flow controllers;
• an upstream purging channel within the objective lens housing of the objective lens;
• an upstream purging outlet connected to the upstream purging channel and configured to purge the gas, wherein the upstream purging outlet is positioned upstream from the scan direction of the sample, wherein as the sample is scanned by the motion sub-system, the gas is moved towards a field of view (FOV) of the objective lens;
• and
• an edge purging module including an edge purging outlet, wherein the edge purging module is configured to provide an additional stream of the gas to the sample when the FOV of the objective lens is at an edge of the sample;
• and
• a computer sub-system communicatively coupled to the motion sub-system, and the purging sub-system, the computer sub-system including one or more processors configured to execute program instructions causing the one or more processors to:
• generate a first set of control signals configured to cause the gas source to provide the gas to the upstream purging channel and the edge purging module;
• generate a second set control signals configured to cause the edge purging module to stop distributing the gas upon the sample being translated a predetermined distance by the motion sub-system;
• and
• generate a third set of signals configured to cause the upstream purging channel to stop distributing the gas upon the sample being fully scanned by the motion sub-system.

An inspection system comprising:

• a computer sub-system communicatively including one or more processors configured to execute program instructions causing the one or more processors to:
• generate a first set of control signals configured to cause a gas source to provide a gas to an upstream purging channel within an objective lens housing and an edge purging module;
• generate a second set control signals configured to cause the edge purging module to stop distributing the gas upon a sample being translated a predetermined distance by a motion sub-system;
• generate a third set of signals configured to cause the upstream purging channel to stop distributing the gas upon the sample being fully scanned by the motion sub-system;
• generate one or more images of the sample based on light detected by a collection sub-system;
• and
• identify one or more sample defects on the sample based on the one or more images of the sample.

A method comprising:

• positioning an edge of a sample at a field of view (FOV) of an objective lens by adjusting a location of a linear stage;
• providing a gas from a gas source to an upstream purging channel and an edge purging module, wherein the upstream purging channel purges a stream of the gas to the sample via an upstream purging outlet, wherein the edge purging module purges an additional stream of the gas to the sample via an edge purging outlet;
• illuminating a sample with one or more illumination beams generated by an illumination source;
• scanning the sample;
• stopping the edge purging module from distributing the additional stream of the gas upon the sample being scanned a predetermined distance;
• stopping the upstream purging channel from distributing the stream of the gas from the upstream purging outlet upon completion of the sample being scanned;
• collecting light illuminated from the sample;
• generate one or more images of the sample based on the light collected from the sample;
• and
• identify one or more sample defects on the sample based on the one or more images generated.