System and method for inspection of a substrate that has a refractive index

A method for inspection of a substrate having a first refraction index being covered by an at least partially transparent layer having a second refractive index, the method comprising:

• defining an apodization scheme in response to a characteristic of the layer;
• directing a beam of radiation, to impinge on the substrate;
• whereas the beam of radiation propagates through an at least partially transparent medium having a first refractive index and the layer having the second refractive index and is subsequently reflected from the substrate;
• whereas the second refractive index differs from a third refractive index and from the first refractive index;
• applying an apodizer to apodize a reflected beam of radiation being reflected from the substrate, in response to the apodization scheme;
• and
• detecting at least a portion of an apodized beam of radiation that passes through the apodizer.

A method for inspection of a substrate having a first refractive index being covered by an at least partially transparent layer having a second refractive index, the method comprising:

• providing an inspection system with an apodizer capable of implementing a plurality of apodization schemes;
• whereas the apodization schemes are responsive to a characteristic of the layer;
• selecting one of the apodization schemes;
• applying the apodizer to apodize a beam of radiation in response to the selected apodization scheme;
• directing the apodized beam of radiation to impinge on the substrate, whereby a plurality of rays are reflected from the substrate;
• directing the apodized beam of radiation, to impinge on the substrate, whereby a plurality of rays are reflected from the substrate;
• whereas the apodized beam of radiation propagates through an at least partially transparent medium having a first refractive index and the layer having the second refractive index and is subsequently reflected from the substrate;
• whereas the second refractive index differs from a third refractive index and from the first refractive index;
• and
• detecting at least one of the reflected rays.

An apparatus for inspection of a substrate having a first refractive index being covered by an at least partially transparent layer having a second refractive index, the apparatus comprising:

• a radiation source, which is adapted to generate a beam of radiation;
• an apodizer, which is adapted to apodize the beam of radiation in response to an apodization scheme;
• whereas the apodization scheme is responsive to a characteristic of the layer;
• an optical objective, which is adapted to direct the apodized beam of radiation to impinge on the substrate, whereby a plurality of rays are reflected from the substrate;
• whereas the apodized beam of radiation propagates through an at least partially transparent medium having a first refractive index and the layer having the second refractive index and is subsequently reflected from the substrate;
• whereas the second refractive index differs from a third refractive index and from the first refractive index;
• and
• a detector, which is adapted to detect at least one of the reflected rays.

An apparatus for inspection of a substrate having a first refractive index, the apparatus comprising:

• a radiation source, which is adapted to generate a beam of radiation;
• an optical objective, which is adapted to direct the beam of radiation to impinge on the substrate, where by a plurality of rays are reflected from the substrate, whereas at least a some of the reflected rays define a reflected beam of radiation;
• whereas the beam of radiation propagates through an at least partially transparent medium having a first refractive index and an at least partially transparent layer having a second refractive index and is subsequently reflected from the substrate;
• whereas the second refractive index differs from a third refractive index and from the first refractive index;
• an apodizer, which is adapted to apodize the reflected beam of radiation in response to an apodization scheme;
• whereas the apodization scheme is responsive to a characteristic of the layer;
• and
• a detector, which is adapted to detect at least one of the reflected rays.