HEMT Passivation Layer Etch Stop Structure

The patent deposits a second passivation layer over the first passivation layer before performing the gate recess etching process. This second passivation layer serves as a protective barrier during etching, preventing etchant from reaching and damaging the compound layer surface. After etching is complete, the second passivation layer is removed, revealing a clean, undamaged compound layer surface that maintains excellent electrical performance.

The second passivation layer acts as an intermediary protective layer between the etching process and the compound layer. It temporarily absorbs the harmful effects of the etchant, allowing the gate recess to be formed while shielding the underlying compound layer from damage. This intermediary layer is then removed after serving its protective purpose.

The patent segments the manufacturing process into distinct stages, each with its own dedicated passivation layer protection. The first passivation layer protects during metal deposition, the second passivation layer protects during gate recess etching, and the third passivation layer provides final protection. This segmentation ensures that each sensitive interface is protected during its specific vulnerable process while allowing other processes to proceed without restriction.

The patent applies preliminary protection strategies for each known damaging process in the manufacturing sequence. Before metal deposition, a first passivation layer is deposited to prevent metal contamination. Before gate recess etching, a second passivation layer is deposited to prevent etch damage. Before final processing, a third passivation layer is deposited. This systematic preliminary protection approach ensures that each interface maintains high quality throughout the multi-step manufacturing process.