Inspection Method and Apparatus, Substrates for use Therein and Device Manufacturing Method

An inspection apparatus comprising:

• illumination optics configured to direct radiation with a first wavelength at a target structure;
• detection optics configured to receive radiation scattered by the target and for forming a spectrum of the scattered radiation;
• a detector configured to convert the spectrum into electrical signals;
• and
• a processor configured to calculate a dimensional characteristic of the structure based on characteristics of one or more spectral components in the detected spectrum having wavelengths different from the first wavelength due to inelastic scattering.

A method of performing a lithographic process comprising:

• forming device structures and at least one metrology target structures on a substrate by said lithographic process;
• measuring a dimensional characteristic of the target structure by:
• directing radiation with a first wavelength at the target structure,
• receiving radiation scattered by the target structure and forming a spectrum of the scattered radiation so as to distinguish one or more spectral components in the spectrum having wavelengths different from the first wavelength due to inelastic scattering by the target structure, and
• calculating a dimensional characteristic of the target structure based on characteristics of the spectral components;
• and
• controlling subsequent processing of the measured substrate in accordance with the measured value of said dimensional characteristic.