Patent ID: 6939209

Claim:
An apparatus for measurement of remaining semiconductor substrate thickness of at least a portion of a semiconductor wafer, said portion having a thickness less than 50 micrometers, said measurement having an accuracy at least as good as about 100 nm, said apparatus comprising: a holder for holding said wafer portion; a light source of broadband emission including wavelengths from visible to IR spectrum, a spectrometer configured to operate at light wavelengths in the range between 700 nm and 1000 nm; a lens assembly to collimate light from said light source into a collimated light beam; a microscope objective lens assembly positioned to focus said collimated light beam onto said wafer portion as incident light at a point of incidence, a portion of said incident light being reflected from said wafer portion, said incident light having a beam spot size at said point of incidence, said microscope objective lens assembly configured to operate in Near InfraRed (NIR) range; means for delivering said light from said light source to said lens assembly to be collimated into said collimated light beam; means for delivering reflected light from said wafer portion to said spectrometer; said lens assembly and said microscope lens assembly configured to provide said beam spot size with a diameter less than 100 microns; an xyz stage assembly, said xyz stage assembly adjustable to provide relative motion between said wafer portion and said microscope lens assembly, to move said point of incidence across said wafer portion, to provide focus adjustment for said objective lens assembly and to provide device navigation; and a computer in communication with said reflectance spectrometer for calculating the remaining thickness of said wafer portion.