PURPOSE: To provide a method for measuring the concentration of hydrogen in a high temperature atmosphere without causing contamination of a heat treatment furnace by monitoring the partial pressure of hydrogen based on t}ae concentration of hydrogen in a monitor crystal.

CONSTITUTION: A silicon crystal fragment and a silicon substrate 5 are heat-treated in a heat treatment furnace 3 thus converting the crystal fragment into a monitor crystal 1. The residual crystal fragment 1 is heat-treated in an atmosphere containing hydrogen under the pressure of 1atm thus producing a hydrogen doped silicon crystal 2. The crystals 1, 2 are further subjected to heat treatment in nitrogen atmosphere to create thermal doners in the crystal. The crystal 1, 2 is split in two and a probe 9a is applied to the split face in order to measure 9 the specific resistance thus determining the thermal doner concentration. A linear relationship is present between the logarithmic values of thermal cloner concentration and hydrogen concentration of the crystal 2 and when the thermal doner concentration of the crystal 1 is fitted, corresponding hydrogen concentration C=3.05×1011 atoms.cm-3 in the crystal 1 is obtained. Partial pressure of hydrogen Pa2×10-6atm is then operated and the hydrogen concentration in the atmosphere of heat treatment process is determined to be 2ppm in the vicinity of a substrate 5.