Metrology and analysis

What is the main reason fine patterns a few tens of nm wide cannot be observed directly with an optical microscope?

  1. ABecause diffraction of light limits resolution (to roughly the wavelength of light)
  2. BBecause optical microscopes show no color
  3. CBecause optical microscopes are too dark
Show answer and explanation

Answer: A. Because diffraction of light limits resolution (to roughly the wavelength of light)

Because of diffraction, the resolution of an optical microscope is limited to about half the wavelength of the light used. Visible light has wavelengths of about 400–700 nm, so patterns a few tens of nm wide cannot be resolved. SEMs and TEMs, which use electron beams with shorter wavelengths, are therefore used.

Practice this topic Back to topic

More Metrology and analysis questions

  1. Which equation is used to determine film stress from the change in wafer bow before and after deposition?
  2. Whereas SIMS measures the atomic concentration of impurities, which method measures the depth distribution of electrically active carrier concentration?
  3. What is the measurement called that monitors a process by measuring product wafers partway through processing on the production line?
  4. Which inspection detects defects such as contact open failures using differences in brightness caused by differences in charging under an electron beam?
  5. When observing insulating samples with an SEM, which is a correct way to prevent charging (charge-up)?