Film thickness measuring method and step measuring method

A step height measuring method comprising:

• projecting white light onto a wafer with a film to be measured whose surface is uneven and sensing a first reflected light intensity from said wafer for each wavelength;
• determining a value of said sensed first reflected light intensity for each wavelength in a form of a first light intensity profile with wavelength as an abscissa axis and light intensity as an ordinate axis;
• projecting said white light onto a reference sample which has the same structure as that of an underlying layer below a film to be measured of said wafer and sensing a second reflected light intensity from said reference sample for each wavelength;
• determining a value of said second reflected light intensity for each wavelength in a form of a second light intensity profile with wavelength as the abscissa axis and light intensity as the ordinate axis;
• calculating a normalized light intensity profile by dividing said first light intensity profile by said second light intensity profile;
• and
• calculating a step height in said film to be measured from said normalized light intensity profile.

A semiconductor device manufacturing method comprising:

• forming a film to be measured on a wafer;
• projecting white light onto said wafer with the film to be measured and sensing a first reflected light intensity from said wafer for each wavelength;
• determining a value of said sensed first reflected light intensity for each wavelength in a form of a first light intensity profile with wavelength as an abscissa axis and light intensity as an ordinate axis;
• projecting said white light onto a reference sample which has the same structure as that of an underlying layer below a film to be measured of said wafer and sensing a second reflected light intensity from said reference sample for each wavelength;
• determining a value of said second reflected light intensity for each wavelength in a form of a second light intensity profile with wavelength as the abscissa axis and light intensity as the ordinate axis;
• calculating a normalized light intensity profile by dividing said first light intensity profile by said second light intensity profile;
• calculating a film thickness of said film to be measured from said normalized light intensity profile;
• and
• if said film thickness of said film to be measured meets a process specification, proceeding to a next process, whereas if said film thickness does not meet said process specification, reexamining a condition for manufacturing said film to be measured.

A film thickness measuring apparatus comprising:

• a lighting optical system which causes a convergent lens to converge and project white light from a white light source onto a wafer with a film to be measured;
• a sensor which senses a reflected light intensity from said wafer obtained as a result of said projection of said white light for each wavelength via a spectroscope;
• and
• a computer which calculates a film thickness of said film to be measured from said sensed reflected light intensity, said computer determining and recording a value of said reflected light intensity for each wavelength in a form of a first light intensity profile with wavelength as an abscissa axis and light intensity as an ordinate axis, using said lighting optical system and said sensor to calculate and record in a form of a second light intensity profile said reflected light intensity from a reference sample which has the same structure as that of an underlying layer below said film to be measured, calculating a normalized light intensity profile by dividing said first light intensity profile by said second light intensity profile, and calculating a film thickness of said film to be measured from said normalized light intensity profile.

A computer program, recorded on a computer-readable medium and configured to measure a film thickness of a film to be measured on a wafer, said computer program comprising:

• projecting white light onto a wafer with a film to be measured and sensing a first reflected light intensity from said wafer for each wavelength;
• determining a value of said sensed first reflected light intensity for each wavelength in a form of a first light intensity profile with wavelength as an abscissa axis and light intensity as an ordinate axis;
• projecting said white light onto a reference sample which has the same structure as that of the underlying layer below said film to be measured of said wafer and sensing a second reflected light intensity from said reference sample for each wavelength;
• determining a value of said second reflected light intensity for each wavelength in a form of a second light intensity profile with wavelength as the abscissa axis and light intensity as the ordinate axis;
• calculating a normalized light intensity profile by dividing said first light intensity profile by said second light intensity profile;
• and
• calculating a film thickness of said film to be measured from said normalized light intensity profile.