Image Number 6 for United States Patent #7854821.
A substrate processing apparatus includes a heat transfer gas supply mechanism to supply a heat transfer gas through a supply passage into a portion between a worktable and a substrate to improve thermal conductivity between therebetween. Under the control of a control section, the pressure inside the supply passage is measured to obtain a pressure measurement value while the substrate is placed on the worktable. Then, a preparatory flow rate of the heat transfer gas to be supplied through the supply passage into the portion between the worktable and substrate is determined, in accordance with the pressure difference between the pressure measurement value and a pressure reference value, prior to a main process to be performed on the substrate. Then, the heat transfer gas is supplied through the supply passage into the portion between the worktable and substrate at the preparatory flow rate, prior to the main process.