Bonding III-V Semiconductor Layers Using Thermal Expansion
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Solution Overview
Problem
The challenge in semiconductor device fabrication is the lattice parameter mismatch and resulting strain between adjacent layers, which limits the thickness and indium concentration of semiconductor materials like indium gallium nitride, leading to defects and undesirable phase separation.
Innovation Solution
The method involves forming a layer of III-V type semiconductor material on a substrate with a specific coefficient of thermal expansion, attaching a bonding substrate with a lower expansion coefficient, and controlling the temperature to maintain the desired lattice parameter, thereby reducing strain and allowing for thicker, higher-indium-content layers without phase separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a layer of III-V type semiconductor material is formed on a substrate, then the semiconductor layer can be grown, but lattice parameter mismatch and strain occur between adjacent layers, limiting the thickness and indium concentration of the semiconductor material
Solution Approach 1:
The patent changes the temperature parameter during bonding to control the lattice parameter of the semiconductor layer. By bonding at an elevated temperature where the substrate has expanded, the semiconductor layer is forced to adopt a larger lattice parameter that matches the strained state, allowing thicker and higher-indium-content layers without relaxation to defective phases.
Solution Approach 2:
The patent exploits the thermal expansion of the substrate to solve the lattice mismatch problem. The substrate is heated to expand its lattice parameter, then the semiconductor layer is bonded to it while in this expanded state. Upon cooling, the substrate contracts but the semiconductor layer maintains its expanded lattice parameter, effectively creating a strain-compensated structure that allows for higher indium content and greater thickness.
2Reliability
If the thickness and indium concentration of semiconductor layers are increased to improve device performance, then higher performance is achieved, but phase separation and defects occur due to lattice strain
Solution Approach 1:
The patent changes the temperature parameter during bonding to control the lattice parameter of the semiconductor layer. By bonding at an elevated temperature where the substrate has expanded, the semiconductor layer is forced to adopt a larger lattice parameter that matches the strained state, allowing thicker and higher-indium-content layers without relaxation to defective phases.
Solution Approach 2:
The patent applies preliminary anti-action by pre-straining the semiconductor layer through temperature-controlled bonding. The layer is bonded to the substrate while both are at an elevated temperature, forcing the semiconductor layer into a strained state that prevents subsequent phase separation. This preliminary straining counteracts the natural tendency toward relaxation and defect formation that would occur at room temperature bonding.
3Manufacturing precision
If temperature is changed to control lattice parameter, then desired lattice parameters are achieved, but temperature control complexity increases
Solution Approach 1:
The patent exploits the thermal expansion of the substrate to solve the lattice mismatch problem. The substrate is heated to expand its lattice parameter, then the semiconductor layer is bonded to it while in this expanded state. Upon cooling, the substrate contracts but the semiconductor layer maintains its expanded lattice parameter, effectively creating a strain-compensated structure that allows for higher indium content and greater thickness.
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 approach enables the fabrication of semiconductor layers with controlled lattice strain and parameters, reducing defects and phase separation, allowing for the growth of thicker indium gallium nitride layers with higher indium content and improved device performance.
Implementation Method 1
heating the substrate and the bonding substrate to an elevated temperature
Implementation Method 2
cooling the substrate and the bonding substrate from the elevated temperature to a lower temperature
Data Source
AI summary
Methods of fabricating semiconductor devices or structures include bonding a layer of semiconductor material to another material at a temperature, and subsequently changing the temperature of the layer of semiconductor material. The another material may be selected to exhibit a coefficient of thermal expansion such that, as the temperature of the layer of semiconductor material is changed, a controlled and/or selected lattice parameter is imparted to or retained in the layer of semiconductor material. In some embodiments, the layer of semiconductor material may comprise a III-V type semiconductor material, such as, for example, indium gallium nitride. Novel intermediate structures are formed during such methods. Engineered substrates include a layer of semiconductor material having an average lattice parameter at room temperature proximate an average lattice parameter of the layer of semiconductor material previously attained at an elevated temperature.