Semiconductor electrical measurement

Semiconductor electrical measurement

  In order to meet the needs of various semiconductor devices, electrical parameters of materials must be measured. These parameters are generally resistivity, carrier concentration, conductivity type, mobility, lifetime, and carrier concentration distribution. Measurement methods include four probes, three probes, extended resistance, CV method and Hall measurement.

     For the resistivity of semiconductor materials, four probes, three probes and extended resistance are generally used. 

     The four-probe method is one that is often used, with simple principles and easy data processing. The measurement range is 10 -3 -10 4  meters. It can distinguish the uniformity of millimeter-level materials. It is suitable for measuring the resistivity of semiconductor materials, special-shaped layers, epitaxial materials and diffusion layers, and ion implantation layers, and can provide a rapid, Non-destructive, more accurate measurement. 

    When the four-probe method is used to measure the resistivity of the epitaxial layer material of the same conductivity type and low resistance substrate, since the current flowing through the material will be short-circuited in the low resistance substrate, the result is that the substrate and the epitaxial layer resistivity are connected in parallel The overall result. At this time, it is necessary to adopt the three-probe method, the extended resistance method, etc. 

    The three-probe method uses the reverse current-voltage characteristics of the contact between the metal probe and the semiconductor material and measures the voltage at the time of breakdown to obtain knowledge of the resistivity of the material. 

    The CV method uses the capacitance characteristics of the PN junction or Schottky barrier in reverse bias to obtain information on the impurity concentration and its distribution in the material. This type of measurement is called the CV measurement technique. This kind of measurement can provide information on material cross-section uniformity and longitudinal impurity concentration distribution, so it has greater advantages than four-probes, three-probes, and so on. Although the extended resistance can also measure the longitudinal distribution, it requires the sample to be angled. However, the CV method can not only measure the distribution of epitaxial materials on the same-type low-resistance substrates, but also measure the distribution of epitaxial materials of special-shaped layers for high-resistance substrates. 

    Hall measurement In the measurement of semiconductor materials, the Hall effect has a wide range of applications. Use it to study the conduction process or transport phenomena of semiconductor materials. It can provide information on the conductivity type of the material, carrier concentration, impurity ionization energy (including deep and shallow level impurities), band gap, mobility and impurity compensation.