Wafers are physically and chemically cleaned using ultra-pure water and chemicals.

Wafers flatness and surface cleanliness (particle-free) are key factors as a substrate for recent leading-edge ULSI devices. Individual wafer flatness and surface particles are measured using specially designed inspection tools to assure wafer quality.

Two probes make ohmic contact with the wafer surface. One is heated 25-100˚C hotter than the other. A voltmeter placed across the probes will measure a potential difference whose polarity indicates whether the material is N or P type.

For N-type sample: The majority carriers are electrons. At the hot probe, the thermal energy of the electrons is higher than the cold probe so the electrons will tend to diffuse away from the hot probe, driven by the temperature gradient. As the electrons diffuse away from the hot probe, they leave behind the positively charged, immobile donor atoms that provided the electrons. The negatively charged mobile electrons tend to build up near the cold probe, which results in the hot probe becoming positive with respect to the cold probe.

For P-type sample: The majority carriers are holes. The polarity of the induced voltage would be reversed.

allow to force the current through the two outer probes and measure the voltage drop with the two inner probes using a high-impedance voltmeter.

Problem with probe contacts: eliminated in the voltage measurement since no current flows through these contacts.

determine the material type, carrier concentration and carrier mobility

When current flow (from left to right), electrons flow in the opposite direction (from right to left) and the magnetic field, B is normally tangential to the current flow. When the electron moves across, they will not be evenly distributed due to the magnetic field. As a result, top and bottom will have a different potential which can be measured.

to measure oxygen and carbon which were introduced from CZ crystal growth process and control them

measures the absorption of infrared energy by the molecules in a sample. Many molecules have vibrational modes that absorb specific wavelengths when they are excited.

By sweeping the wavelength of the incident energy and detecting which wavelengths are absorbed, a characteristic signature of the molecules present is obtained.