Composite Substrate for GaN HEMT Thermal Stability

The patent employs a composite substrate comprising a base substrate and a conductive layer formed thereon. The base substrate provides mechanical support and thermal mass, while the conductive layer (made of materials such as titanium, aluminum, or tungsten) enhances heat absorption and thermal conductivity. This composite structure resolves the contradiction by achieving superior thermal stability without overly complicating the manufacturing process, as the conductive layer can be deposited using standard sputtering or evaporation techniques.

The conductive layer serves multiple functions simultaneously: it acts as a thermal management component by absorbing and distributing heat, serves as an electrical contact layer for subsequent electrode formation, and provides a stable foundation for dielectric layer adhesion. This multi-functionality addresses the contradiction by improving thermal stability while avoiding the need for additional separate components that would increase device complexity.

The patent creates a composite substrate where a conductive layer is deposited on an electrically insulating base substrate. The base substrate (such as silicon oxide, silicon nitride, or sapphire) maintains electrical insulation properties, while the conductive layer (titanium, aluminum, or tungsten) provides enhanced heat absorption and thermal conductivity. This composite approach resolves the contradiction by combining materials with complementary properties.

The conductive layer is applied locally to the surface of the base substrate where thermal management is most critical, particularly in regions underlying active device components. This localized application optimizes heat absorption where needed while preserving the electrical insulation properties of the base substrate in other areas, thereby resolving the contradiction between thermal performance and electrical insulation.

The patent introduces a dielectric layer as an intermediary between the exposed conductive layer and the external environment. This dielectric layer (such as silicon oxide or silicon nitride) serves as a protective barrier that prevents contamination and oxidation of the conductive layer while allowing electrical contact to be established through controlled openings or contacts. This resolves the contradiction by protecting the conductive layer from harmful factors while maintaining its electrical functionality.

The conductive layer is deposited with sufficient thickness and adhesion to resist oxidation and contamination during subsequent processing steps before final device assembly. Additionally, the processing environment is controlled (e.g., using inert atmospheres or vacuum conditions) to prevent oxidation of the conductive layer in advance, thereby preemptively countering the harmful effects of contamination and oxidation while maintaining electrical contact capability.

The patent segments the patterning process into multiple stages: first forming a coarse pattern using photolithography, then refining and completing the pattern using selective etching or deposition processes. This segmentation allows the high-precision photolithography step to be minimized in scope and duration, while subsequent faster processes complete the patterning, thereby resolving the contradiction between precision and productivity.

The patent performs preliminary patterning actions by pre-forming guide structures, alignment marks, or rough patterns using photolithography before final device fabrication. These preliminary patterns serve as templates for subsequent self-aligned or template-guided processes that can proceed more rapidly, thereby maintaining high precision while improving overall manufacturing speed and productivity.