Substrate temperature control method and plasma processing apparatus

A substrate temperature control method comprising:

• disposing a substrate on a substrate disposing surface of a placing table provided in a vacuum processing chamber, the placing table being configured to be cooled or heated;
• supplying a heat conduction gas between a rear surface of the substrate and the substrate disposing surface of the placing table to control a temperature of the substrate;
• detecting a pressure of the heat conduction gas;
• comparing the detected pressure value with a set pressure value;
• controlling the supply of the heat conduction gas so that the detected pressure value becomes the set pressure value;
• and
• when the pressure of the heat conduction gas is set to a low pressure value that is lower than a predetermined lowest limit pressure value and the temperature of the substrate is controlled by suppressing the heat exchange between the substrate and the placing table, alternately repeating a first period where the set pressure value is set to be a first set pressure value that is higher than the low pressure value and equal to or higher than the predetermined lowest limit pressure value and a second period where the set pressure value is set to be a second set pressure value that is lower than the low pressure value,
• wherein the predetermined lowest limit pressure value is a minimum value for the heat exchange between the substrate and the placing table using the heat conduction gas.