High speed inspection of a sample using coherence processing of scattered superbroad radiation

An inspection apparatus for inspecting a sample which comprises:

• a source of radiation which outputs:
• (a) superbroad inspection radiation having a frequency spectrum with an inspection width and (b) one or more reference radiation outputs, each of the one or more reference radiation outputs having a reference frequency spectrum with a reference width that is less than or substantially equal to the inspection width;
• an inspection applicator apparatus which applies the inspection radiation as input to the sample;
• an inspection collection apparatus which collects at least a portion of the inspection radiation that is scattered by the sample and applies at least a portion of the scattered inspection radiation as input to a dispersal apparatus;
• a reference collection apparatus which applies radiation from the one or more reference radiation outputs as input to the dispersal apparatus;
• wherein the dispersal apparatus applies radiation from the scattered inspection radiation as input to a plurality of coherence processors and applies radiation from the one or more reference radiation outputs to the plurality of coherence processors;
• wherein the width of the frequency spectrum of the radiation from the scattered inspection radiation that is applied as input to the coherence processors and the width of the frequency spectrum of the radiation from the one or more reference radiation outputs that is applied as input to the coherence processors satisfy one of the following:
• the width of the frequency spectrum of the radiation from the scattered inspection radiation is substantially the same as the inspection width and the width of the frequency spectrum of the radiation from the one or more reference radiation outputs is less than the inspection width;
• or
• the width of the frequency spectrum of the radiation from the scattered inspection radiation is less than the inspection width and the width of the frequency spectrum of the radiation from the one or more reference radiation outputs is substantially the same as the inspection width;
• or
• the width of the frequency spectrum of the radiation from the scattered inspection radiation is less than the inspection width and the width of the frequency spectrum of the radiation from the one or more reference radiation outputs is less than the inspection width.

A method of inspecting a sample which comprises the steps of:

• generating superbroad inspection radiation having a frequency spectrum with an inspection width and reference radiation;
• applying the inspection radiation to the sample;
• collecting inspection radiation which is scattered by the sample;
• detecting a plurality of coherent interferences between radiation from the reference radiation and the scattered inspection radiation;
• wherein the width of the frequency spectrum of the radiation from the scattered inspection radiation and the width of the frequency spectrum of the radiation from the reference radiation satisfy one of the following:
• the width of the frequency spectrum of the radiation from the scattered inspection radiation is substantially the same as the inspection width and the width of the frequency spectrum of the radiation from the reference radiation is less than the inspection width;
• or
• the width of the frequency spectrum of the radiation from the scattered inspection radiation is less than the inspection width and the width of the frequency spectrum of the radiation from the reference radiation is substantially the same as the inspection width;
• or
• the width of the frequency spectrum of the radiation from the scattered inspection radiation is less than the inspection width and the width of the frequency spectrum of the radiation from the reference radiation is less than the inspection width.