Comparison of far field characterisation of DOEs with a goniometric DUV-scatterometer and a CCD-based system

Abstract

We have measured far field diffraction patterns of different diffractive optical elements at an illumination wavelength of 193 nm using a new type of goniometric DUV (deep ultraviolet) scatterometer. This system offers both a high dynamic range and angular resolution. The scatterometer is especially suitable to analyse weak background light like stray light and local variations of the diffraction patterns over the DOEs (diffractive optical element). The measurement results are compared with measurements using a CCD (chargecoupled device)-based imaging DOE measurement system. An excellent agreement of the measured far field distributions is demonstrated.

Analytical calculation on the determination of steep side wall angles from far field measurements

“…Nonetheless, optical techniques using light are still the preferred choice because of their ease of implementation and measurement speed, along with the important property of being non-destructive. A known technique for this purpose is optical scatterometry [7][8][9][10][11]. In this technique, the test structure is described by a few shape parameters such as height (h), middle critical dimension, and SWA that are retrieved by solving an inverse problem using the measured scattered light intensities as data and combining them with a priori knowledge of the system.…”

Interferometric coherent Fourier scatterometry: a method for obtaining high sensitivity in the optical inverse-grating problem

“…Goniometric scatterometry [13,14] is probably the most well known angular scatterometry technique. As illustrated in figure 1(a), plane waves corresponding to a certain set of incident angles interact with the grating one by one and the intensities of the reflected orders are measured for all combinations of orthogonal states of the polarizers in the incident and scattered beams.…”

Phase retrieval between overlapping orders in coherent Fourier scatterometry using scanning

“…The inverse problems in scatterometry belongs to the family of ill-posed problems in electromagnetism, but by using a-priori information about the scatterer, reconstruction of the grating is possible to a certain extent. IOS is an established method of lithographic process inspection [3]- [5], but with continuing shrinkage of the features written by lithographic machines, a more sensitive, repeatable and robust method for semiconductor metrology is desirable.…”