System for directly measuring the depth of a high aspect ratio etched feature on a wafer

A system for directly measuring the depth of a high aspect ratio etched feature on a wafer having an etched surface and a non-etched surface, said system comprising;

• a) an infrared reflectometer comprising:
• (1) a swept laser having means for producing a wavelength that is swept in time across a range of wavelengths, a trigger signal and a clock signal,
• (2) a fiber circulator having a first input that is applied the wavelengths from said swept laser, a second input, a first light output and a second light output,
• (3) a collimator that is applied the second light output from said fiber circulator and that produces a collimated light output that is applied to the second input on said fiber circulator,
• (4) an objective lens that interfaces with the collimator and that is positioned to face the non-etched surface of the wafer, wherein from the lens is emitted a focused incident light that is applied to the non-etched surface of the wafer, wherefrom the wafer is emitted a reflected light that is applied to said objective lens,
• (5) a photodetector that is applied the first light output from said fiber circulator and that produces an analog spectrum optical frequency signal,
• b) an analog to digital converter (ADC) that functions as a data acquisition device, said ADC having a first input and a second input that are applied respectively the trigger signal and the clock signal from the swept laser, wherein said ADC further having a third input that is applied the analog spectrum optical frequency signal that is applied from the photodetector, wherein said ADC produces a corresponding digital data signal,
• c) a computer, in combination with software, having means for processing the digital data signal applied from the ADC and to produce a display signal that portrays on a display the depth of the high aspect ratio etched feature on the wafer, and
• d) a wafer holding fixture having means for being laterally displaced and means for positioning the non-etched surface of the wafer facing the objective lens on said infrared reflectometer.

A system for directly measuring the depth of a high aspect ratio etched feature on a wafer having an etched surface and a non-etched surface, said system comprising:

• a) a broadband incoherent infrared source (BIIS) having means for producing an incoherent light source,
• b) a fiber circulator having a first input that is applied the incoherent light signal from said BIIS, a second input, a first light output and a second light output,
• c) a collimator that is applied the second light output from said fiber circulator and that produces a collimated light output that is applied to the second input on said fiber circulator,
• d) an objective lens that interfaces with the collimator and that is positioned to face the non-etched surface of the wafer, wherein from the lens is emitted a focused incident light that is applied to the non-etched surface of the wafer, wherefrom the wafer is emitted a reflected light that is applied to said objective lens,
• e) a spectrometer that is applied the light signal from said fiber circulator and that produces a light distribution signal,
• f) a computer, in combination with software, having means for processing the light distribution signal applied from said spectrometer and to produce a digital data signal that portrays on a display the depth of the high aspect ratio etched feature on the wafer, and
• g) a wafer holding fixture having means for being laterally displaced and means for positioning the non-etched surface of the wafer facing the objective lens.