Method and apparatus for thickness decomposition of complicated layer structures
First Claim
1. Thickness measurement apparatus for measuring layer thicknesses on patterned areas of a semiconductor wafer, the apparatus comprising:
- a spectrum analyzer for obtaining reflection data taken from a patterned area and obtaining therefrom a frequency spectrum, a peak detector, associated with said spectrum analyzer, for searching said spectrum to find peak frequencies within said spectrum, said peak detector being operable to restrict said search to regions corresponding to peak frequencies found in a learning stage, a frequency filter, associated with said peak detector, for filtering said spectrum about said peak frequencies, and a maximum likelihood fitter for using parameters obtained in said learning stage to carry out maximum likelihood fitting of said filtered spectrum to obtain at least said layer thicknesses
3 Assignments
0 Petitions
Accused Products
Abstract
Thickness measurement apparatus for measuring layer thicknesses on patterned areas of a semiconductor wafer, comprises: a spectrum analyzer for obtaining reflection data taken from a patterned area and obtaining therefrom a frequency spectrum, a peak detector for searching the spectrum to find peak frequencies within said spectrum, the search being restricted to regions corresponding to peak frequencies found in an earlier learning stage, a frequency filter, associated with the peak detector, for filtering the spectrum about said peak frequencies, and a maximum likelihood fitter for using parameters obtained in the learning stage to carry out maximum likelihood fitting of said filtered spectrum to obtain the desired layer thicknesses. By carrying out maximum likelihood fitting using parameters obtained beforehand in a high resolution non-real time learning stage, it is possible to provide high resolution results in real time.
-
Citations
26 Claims
-
1. Thickness measurement apparatus for measuring layer thicknesses on patterned areas of a semiconductor wafer, the apparatus comprising:
-
a spectrum analyzer for obtaining reflection data taken from a patterned area and obtaining therefrom a frequency spectrum, a peak detector, associated with said spectrum analyzer, for searching said spectrum to find peak frequencies within said spectrum, said peak detector being operable to restrict said search to regions corresponding to peak frequencies found in a learning stage, a frequency filter, associated with said peak detector, for filtering said spectrum about said peak frequencies, and a maximum likelihood fitter for using parameters obtained in said learning stage to carry out maximum likelihood fitting of said filtered spectrum to obtain at least said layer thicknesses - View Dependent Claims (2, 3, 4, 5, 6)
-
-
7. Thickness measurement apparatus for measuring layer thicknesses on patterned areas of a semiconductor wafer, the apparatus comprising:
-
a) an input spectrum analyzer for obtaining a reflection spectrum from respective patterned areas of semiconductor wafers, b) a learn mode unit comprising;
a peak detector, associated with said spectrum analyzer, for searching said spectrum to find peak frequencies within said spectrum, said peak detector being operable to restrict said search to regions corresponding to expected thicknesses of layers in said patterned areas, a frequency filter, associated with said peak detector, for filtering said spectrum about said peak frequencies, a high resolution spectrum analyzer for obtaining parameters from said filtered spectrum for use in maximum likelihood fitting, and a maximum likelihood fitter for using said parameters to carry out maximum likelihood fitting of said filtered spectrum to obtain at least learn mode layer thicknesses and c) a run mode unit comprising;
a peak detector, associated with said spectrum analyzer, for searching said spectrum to find peak frequencies within said spectrum, said peak detector being operable to restrict said search to regions corresponding to peak frequencies found by said learn mode unit, a frequency filter, associated with said peak detector, for filtering said spectrum about said peak frequencies, and a maximum likelihood fitter for using said parameters obtained by said learn mode unit to carry out maximum likelihood fitting of said filtered spectrum to obtain said layer thicknesses. - View Dependent Claims (8)
-
-
9. A method for measuring layer thicknesses on patterned areas of a semiconductor wafer, the method comprising:
-
obtaining reflection data taken from a patterned area, obtaining therefrom a frequency spectrum, searching said spectrum to find peak frequencies within said spectrum said search being restricted to regions corresponding to peak frequencies found in a learning stage, filtering said spectrum about said peak frequencies, and using parameters obtained in said learning stage to carry out maximum likelihood fitting of said filtered spectrum to obtain said layer thicknesses. - View Dependent Claims (10, 11, 12, 13, 14)
-
-
15. Method for measuring layer thicknesses on patterned areas of a semiconductor wafer, comprising:
-
a) a stage of obtaining a reflection spectrum from respective patterned areas of semiconductor wafers, b) a learning stage comprising;
searching said spectrum to find peak frequencies within said spectrum, whilst restricting said search to regions corresponding to expected thicknesses of layers in said patterned areas, filtering said spectrum about said peak frequencies, obtaining parameters from said filtered spectrum for use in maximum likelihood fitting, and using said parameters to carry out maximum likelihood fitting of said filtered spectrum to obtain learn mode layer thicknesses; and
c) a run stage comprising;
searching said spectrum to find peak frequencies within said spectrum, whilst restricting said search to regions corresponding to peak frequencies found in said learning stage, filtering said spectrum about said peak frequencies, and using said parameters obtained in said learning stage to carry out maximum likelihood fitting of said filtered spectrum to obtain said layer thicknesses. - View Dependent Claims (16)
-
-
17. Apparatus for controlling a semiconductor wafer production line, said production line having a plurality of stations, successive stations being for carrying out successive processes on wafers to add features to said wafers, at least one of said stations having a measuring unit for providing measurements of layers on a patterned surface part of a respective wafer, the measuring unit comprising:
-
a spectrum analyzer for obtaining reflection data taken from a patterned area and obtaining therefrom a frequency spectrum, a peak detector, associated with said spectrum analyzer, for searching said spectrum to find peak frequencies within said spectrum, whilst restricting said search to regions corresponding to peak frequencies found in a learning stage, a frequency filter, associated with said peak detector, for filtering said spectrum about said peak frequencies, and a maximum likelihood fitter for using parameters obtained in said learning stage to carry out maximum likelihood fitting of said filtered spectrum to obtain said layer thicknesses, said layer thicknesses being usable as control signals for said wafer production line. - View Dependent Claims (18, 19, 20, 21, 22, 23)
-
-
24. Apparatus for controlling a semiconductor wafer production line, said production line having a plurality of stations, successive stations being for carrying out successive processes on wafers to add features to said wafers, at least one of said stations having a measuring unit for providing measurements of layers on a patterned surface part of a respective wafer, the measuring unit comprising:
-
a) an input spectrum analyzer for obtaining a reflection spectrum from respective patterned areas of semiconductor wafers, b) a learn mode unit comprising;
a peak detector, associated with said spectrum analyzer, for searching said spectrum to find peak frequencies within said spectrum, whilst restricting said search to regions corresponding to expected thicknesses of layers in said patterned areas, a frequency filter, associated with said peak detector, for filtering said spectrum about said peak frequencies, a high resolution spectrum analyzer for obtaining parameters from said filtered spectrum for use in maximum likelihood fitting, and a maximum likelihood fitter for using said parameters to carry out maximum likelihood fitting of said filtered spectrum to obtain learn mode layer thicknesses;
and c) a run mode unit comprising;
a peak detector, associated with said spectrum analyzer, for searching said spectrum to find peak frequencies within said spectrum whilst restricting said search to regions corresponding to peak frequencies found by said learn mode unit, a frequency filter, associated with said peak detector, for filtering said spectrum about said peak frequencies, and a maximum likelihood fitter for using said parameters obtained by said learn mode unit to carry out maximum likelihood fitting of said filtered spectrum to obtain said layer thicknesses said layer thicknesses being usable as control signals for said wafer production line. - View Dependent Claims (25, 26)
-
Specification