Study on thermal contact conductance in vacuum - Effect of surface roughness on contact surface

In semiconductor manufacturing processes, precise temperature control of the wafer is required to obtain high process performance. For this purpose, the relationship between the contact surface roughness and the thermal contact conductance was evaluated by using an experimental apparatus to simulate contact between the wafer and the stage in vacuum. As a result, when the gas flow between the contact surfaces was a free molecular flow (Kn > 10), the gas component of the thermal contact conductance was not affected by the contact surface roughness but was proportional to the gas pressure. Furthermore, as the contact surface roughness decreased, the free molecular flow state remained even under high gas pressure owing to a decrease in the clearance between the contact surfaces. Therefore, a robust contact surface with respect to a change over time in the surface roughness and having high thermal contact conductance was realized by reducing the contact surface roughness and setting a higher gas pressure in the free molecular flow region. © 2019 Japan Society for Precision Engineering. All rights reserved.