Ceramic electrode materials for electrostatic chuck applications

In general, Electrostatic chuck (ESC) was used to fix and clamp the silicon wafer with electrostatic force in the semiconductor fabrication process. Recently, due to their excellent chemical and plasma stability and high thermal conductivity, sintered ceramics has been used as an insulator material in the configuration of ESC. However, metals of high melting point, such as Mo, W, still used for electrode materials. Because of the thermal mismatch between metal electrode and ceramic insulator, micro cracks were produced at the interface during sintering process of ceramic or its operation process with high temperature, which leads to reduce the life time of ESC. To improve the compatibility between metal and ceramic, mesh type metal electrode was used in ESC but this type of electrode results in inhomogeneous electrostatic force. Homogeneous clamping force is very important to determine the final quality of semiconductor. We have investigated a ceramic electrostatic chuck composed of conducting ceramic electrode of titanium nitride instead of metal electrode. Aluminum nitride was added to titanium nitride to control the thermal expansion coefficient. This composite electrode shows not only a good electrical conductivity but also an excellent compatibility to dielectric layer. Compatibility between the electrode and dielectric layer enable to design the electrode with continuous sheet type which leads to homogeneous electrostatic force. Electrostatic force of ceramic ESC with conducting ceramic electrode was about 1700g(f)/4inch wafer when the applied voltage was DC 3kV.