Tapered Gate Contact Openings for Uniform Transistor Etching

The patent applies local quality by implanting ions selectively into the gate dielectric cap material at specific locations and depths. This creates regions with different etch selectivity - the doped regions resist etching while undoped regions etch normally. This local modification of material properties allows different parts of the gate contact opening to etch at different rates, compensating for depth loading effects and producing uniform, vertical sidewalls without tiger-tooth recesses.

The patent changes the physical and chemical parameters of the gate dielectric cap by introducing dopants through ion implantation. This alters the etch selectivity parameter of the material, creating a gradient of etch resistance from the surface downward. By controlling implantation dose, energy, and angle, the patent modifies the etching behavior to achieve uniform depth across the gate contact opening profile.

The patent applies preliminary action by performing ion implantation into the gate dielectric cap before the etching process. This preparatory step pre-modifies the material properties in the critical region, so that when etching occurs, the doped regions automatically provide the desired etch resistance. This advance preparation eliminates the need for complex in-situ corrections during etching and simplifies the overall process control.

The doped regions in the gate dielectric cap serve as an intermediary element between the etching process and the gate contact opening formation. These intermediate doped zones act as etch-resistant barriers that mediate the interaction between the etchant and the underlying structures, preventing direct aggressive etching of the gate spacers and ensuring uniform opening profiles.