Patent ID: 7477388
Filing Date: 2009-01-13
Classification: G01N

Abstract:
1. A method of investigating a sample which comprises a sample system SS having: front FS and back BS sides, with a beam of electromagnetic radiation EMI which impinges upon said front side FS thereof at an oblique angle of incidence θ, said method eliminating the effects of reflection from the back side BS of said sample system SS in a beam of electromagnetic radiation EMR which reflects from the front side of said sample system SS, said method comprising: providing an ellipsometer or polarimeter comprising: said sample system SS comprising a substrate SUB with a surface SUR on the front side thereof; placing a mask M adjacent to surface SUR of said front side of said sample system SS, said mask M having a hole H therein with an effective diameter D which is by the equations: where T′ is the combined thickness of the mask M and its offset T″ from the surface of said sample system SS and θ is said oblique angle of incidence at which said beam of electromagnetic radiation EMI impinges upon said front side BS FS of said sample system SS, and where T is the thickness of said sample system SS and θ′ is an oblique angle of incidence at which said beam of electromagnetic radiation EMI impinges upon said back side BS of said sample system SS; causing an incident beam of electromagnetic radiation EMI provided by said source of a beam electromagnetic radiation LS, to pass through said polarizer P and impinge upon the surface SUR of the front side of said sample system SS at an oblique angle of incidence θ, such that said incident electromagnetic beam EMI reflects from the surface SUR of said front side of said sample system SS as reflected electromagnetic beam EMR and then passes through said analyzer A and enters said detector DET, said reflected electromagnetic beam EMR having no component therein which reflected from the back side BS of said sample system SS as a result of the blocking thereof by said mask M; and causing said reflected beam of electromagnetic radiation EMR which enters said detector DET to be analyzed.