Uncertainty evaluation of diameter measurement in float-zone crystal growth production

Float-zone crystal growth is a method for manufacturing silicon crystals with higher purity and higher resistivity due to crucible-free intrinsic. Diameter measurement of both silicon polycrystalline crystal and monocrystalline crystal using vision system technologies plays a significant role in float-zone silicon crystal growth production yield. The correct measurement evaluation is important since low measurement quality can propagate errors in the diameter control system, thus negatively affect the properties of the growing crystal. Therefore, it is essential to obtain diameter measurements with high accuracy as well as with relatively low uncertainty. Targeted to float-zone silicon crystal growth, the paper presents the uncertainty evaluation of diameter measurements from digital images following the Guide to the Expression of Uncertainty in Measurement (GUM). The uncertainty of diameter measurements of a cylindrical gauge was assessed in the test bench simulating float-zone crystal growth production. The resulting uncertainty of the measured diameter of 203.85 mm was 0.26 mm without considering the uncertainty contribution from thermal expansion.