Optical measurements of patterned structures

A method for thickness mapping of a patterned article containing a plurality of different pattern elements located at different sites, each including a stack of layers, the method comprising the steps of:

• providing an optical model based on a set of parameters corresponding to predetermined characteristics of the article, wherein said set includes inter alia parameters corresponding to geometrical characteristics of the pattern elements, said optical model being capable of generating theoretical data indicative of spectral response of the article;
• preparing reference data containing a plurality of sets of parameters for at least some of said different pattern elements;
• taking spectral measurements of light response at selected sites of said patterned article and generating measured data;
• optimizing the optical model by varying said parameters' sets;
• and
• analyzing the theoretical spectral responses obtained through the optimized optical model and from the measured data, in order to determine therefrom the thicknesses at the selected sites, and generating the thickness map.

A method for determining a surface profile of a patterned article containing a plurality of different pattern elements located at different sites, each including a stack of layers, the method comprising the steps of;

• providing an optical model based on a set of parameters corresponding to predetermined characteristics of the article, wherein said set includes inter alia parameters corresponding to geometrical characteristics of the pattern elements, said optical model being capable of generating theoretical data indicative of spectral response of the article;
• preparing reference data containing a plurality of sets of parameters for at least some of said different pattern elements;
• taking spectral measurements of light response at selected sites of said patterned article and generating measured data;
• optimizing the optical model by varying said parameters' sets;
• and
• analyzing the theoretical spectral responses obtained through the optimization and the measured data, in order to determine therefrom the desired characteristics at the selected sites, and calculating the surface profile from said characteristics.

An optical profilometer for determining a surface profile of a patterned article containing a plurality of pattern elements located at different sites, each including a stack of layers, the optical profilometer comprising:

• a measuring unit including a spectrophotometer that determines spectral response of a measurement site on the article and generates spectral measured data;
• a memory for storing an optical model based on a set of parameters corresponding to predetermined characteristics of the article, wherein said set includes inter alia parameters corresponding to geometrical characteristics of the pattern elements, and said optical model is capable of generating theoretical data indicative of spectral response of the article, said memory storing a reference data containing a plurality of sets of parameters for at least some of said different pattern element;
• and
• a processing unit coupled to the measuring unit for receiving the spectral measured data, optimizing the optical model by various parameters' sets, analyzing the theoretical spectral responses obtained through the optimization and the measured data, in order to determine therefrom the desired characteristic at selected sites, and calculating the surface profile from said characteristic.