InGaAs HEMTs with T-gate electrodes formed by multi-layer SiCN molds

We report a method to control the shape of T-gates precisely by using multi-layer SiCN molds. The SiCN molds consist of a series of SiCN thin films with gradually changed etching properties. The SiCN was deposited by plasma-enhanced chemical vapor deposition using hexamethyldisilazane (HMDS) vapor. An optimized deposition condition of SiCN molds enables us to achieve more precisely control in the T-gate shape such as the stem angle. The SiCN molds technique was applied to the fabrication of T-gates in InGaAs high electron mobility transistors (HEMTs). Two types of HEMTs using the SiCN molds with different deposition conditions were fabricated. The detail analysis of the HEMTs indicates that the difference in the parasitic gate delay and gate resistance reflects the T-gate shapes.