Modulus-enforced probe
Apparatus and methods for forming an image of an object which involves focusing partially to fully spatially-coherent radiation onto a sample and collecting the resulting scattered radiation (the “standard data set”) on an array detector. In addition to the standard dataset, an additional measurement or plurality of measurements is made of a relatively-unscattered beam, using the array detector, which comprises the “modulus enforced probe (MEP) dataset”. This MEP dataset serves as an extra constraint, called the MEP constraint, in the phase retrieval algorithm used to reconstruct the image of the object.
1. A method of determining spatially-resolved, complex scattering properties of a sample, comprising the steps of:
a. providing at least partially spatially-coherent radiation in the form of an incident beam;
b. delivering the incident beam onto the sample to produce scattered radiation;
c. collecting and recording the scattered radiation with an array detector, forming a standard dataset;
d. collecting and recording relatively unscattered radiation on the array detector, forming a MEP dataset;
e. using the standard dataset and the MEP dataset to calculate complex scattering properties of the sample via a phase retrieval method by constraining an illumination profile using the MEP dataset.
2. The method of claim 1 , where the wavelength of the radiation is EUV.
3. The method of claim 1 , wherein step 1 , includes the step of generating light via high harmonic generation.
4. The method of claim 1 , where the standard dataset includes data from one or more of the following types of datasets: ptychographic, through-focus, tomographic, diffraction tomographic, dynamic, holographic, multimode, mutually-incoherent multimode, Fourier Ptychographic, STXM, SRXM, SEM, TEM, STEM, or other CU or point-scanning datasets.
5. The method of claim 1 wherein step 1a, further provides radiation having multiple self- or mutually-incoherent modes.
6. The method of claim 5 wherein the multiple incoherent modes comprise one of the following: differing wavelengths; differing polarizations; varying time delays, orthogonal beam profiles and partial spatial coherence.
7. The method of claim 5 wherein step 1a provides multiple incoherent modes simultaneously.
8. The method of claim 5 wherein step 1a provides multiple incoherent modes sequentially.
9. The method of claim 5 , wherein step 1a provides multiple spatial modes of radiation; wherein step 1c further includes the step of collecting scattered radiation for the multiple spatial modes; and wherein step 1d further includes the step of collecting substantially unscattered radiation for the multiple spatial modes.
10. The method of claim 1 , wherein step 1a further provides radiation that varies with time as step 1c is performed, and wherein step 1d further includes the step of collecting substantially unscattered radiation at various times.
11. The method of claim 1 , wherein step 1d includes the step of delivering the incident beam onto a portion of the sample having known scattering properties.
12. The method of claim 11 , wherein the portion of the sample is substantially not spatially-varying.
13. The method of claim 11 , wherein the portion of the sample is substantially periodic.
14. The method of claim 1 , wherein the MEP dataset is calculated from the standard dataset.
15. The method of claim 14 , wherein the calculation includes the step of taking an average over the scattered radiation and applying a threshold to a resulting image.
16. The method of claim 1 , further including the step of determining the power in the relatively unscattered radiation, wherein step 1e includes the step of using this measurement to constrain beam power.
17. The method of claim 1 , wherein step 1e further includes the step of constraining the illumination profile using a single diffraction pattern phase retrieval algorithm, including: Error Reduction, RAAR, HIO, HPR, Difference Map, Saddle-Point Optimization.