Direct GaN-Diamond Bonding via Van der Waals Forces
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Solution Overview
Problem
Existing semiconductor structures using diamond heat sinks are inefficient in heat removal due to the presence of thermal barriers such as interlayers between the semiconductor chip and the diamond, particularly in GaN-based devices, which limit effective heat conduction.
Innovation Solution
Direct bonding of a GaN epitaxial layer to a diamond substrate using Van der Waals forces without any adhesives or interlayers, facilitated by polishing and re-nucleation processes to create a smooth surface with diamond material in the valleys, allowing for enhanced heat conduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an interlayer (such as Si layer or oxide glue layer) is used between GaN and diamond for bonding, then the bonding process is simplified and manufacturing is easier, but thermal conductivity is reduced due to the thermal barrier effect of the interlayer
Solution Approach 1:
The patent removes the interlayer (Si layer or oxide glue layer) from the bonding structure, achieving direct bonding between GaN and diamond. This extraction of the thermal barrier layer eliminates the thermal resistance it introduces, thereby improving heat conduction efficiency while maintaining bonding capability through direct interface contact.
Solution Approach 2:
The patent creates a composite structure consisting of GaN directly bonded to diamond, forming a heterostructure that combines the semiconductor properties of GaN with the exceptional thermal conductivity of diamond. This direct composite interface eliminates intermediate layers and maximizes thermal transfer between the two materials.
2Adaptability or versatility
If the semiconductor junction is located far from the diamond heat spreader, then device design flexibility is improved, but heat removal efficiency is reduced
Solution Approach 1:
The patent removes the thermal barrier interlayer that previously forced designers to place the junction farther from the heat spreader. By eliminating this thermal resistance, the system can achieve effective heat removal even with optimized junction-to-diamond spacing, thus resolving the conflict between design flexibility and thermal performance.
3Strength
If a thick interlayer (such as 10-20 μm Si layer) is used for bonding, then mechanical strength and bonding reliability are improved, but thermal conductivity is significantly reduced
Solution Approach 1:
The patent extracts and removes the thick Si interlayer (10-20 μm) that provided mechanical bonding strength but acted as a thermal barrier. By eliminating this layer entirely and achieving direct GaN-diamond bonding, the system maintains structural integrity through direct interface bonding while eliminating the thermal resistance that the thick interlayer introduced.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method significantly improves heat dissipation from the semiconductor junction by eliminating thermal barriers, resulting in more efficient heat removal and improved thermal conductivity.
Implementation Method 1
heat removal from the semiconductor structure GaN is substantially improved
Implementation Method 2
The GaN epitaxial layer is directly bonded to the diamond substrate using only Van der Waals forces
Data Source
AI summary
A semiconductor structure is bonded directly to a diamond substrate by Van der Waal forces. The diamond substrate is formed by polishing a surface of diamond to a first degree of smoothness; forming a material, such as diamond, BeO, GaN, MgO, or SiO2 or other oxides, over the polished surface to provide an intermediate structure; and re-polishing the material formed on the intermediate structure to a second degree of smoothness smoother than the first degree of smoothness. The diamond is bonded to the semiconductor structure, such as GaN, by providing a structure having bottom surfaces of a semiconductor on an underlying material; forming grooves through the semiconductor and into the underlying material; separating semiconductor along the grooves into a plurality of separate semiconductor structures; removing the separated semiconductor structures from the underlying material; and contacting the bottom surface of at least one of the separated semiconductor structures to the diamond substrate.