Stacked Nitride Semiconductor Warpage Reduction
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Solution Overview
Problem
The fabrication of stacked nitride-compound semiconductor structures faces challenges due to warpage caused by thermal expansion coefficient differences between nitride-compound semiconductors and substrates, leading to crystalline defects and difficulties in maintaining substrate flatness, especially with silicon substrates which react strongly with gallium, resulting in residue issues and degraded device characteristics.
Innovation Solution
A method involving the formation of first and second nitride-compound semiconductor layers on opposing surfaces of a substrate, with intermediate protection films to balance thermal stress and prevent deposition substance attachment, using silicon oxide and silicon nitride films for protection and easy removal of deposition substances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If deposition substances are removed by chemical treatment, then deposition substances can be removed from substrate surface, but nitride-compound semiconductor shows strong resistance to chemicals making sufficient removal difficult
Solution Approach 1:
The patent changes the physical state and chemical properties of the substrate surface by forming a silicon oxide layer through oxidation treatment. This transforms the chemically resistant nitride-compound semiconductor surface into a silicon oxide surface that is highly susceptible to chemical etching, enabling effective removal of deposition substances while preserving the underlying semiconductor structure.
Solution Approach 2:
The patent introduces a silicon oxide layer as an intermediary between the deposition substances and the nitride-compound semiconductor. This intermediary layer serves as a sacrificial barrier that can be easily removed by chemical treatment, allowing deposition substances to be eliminated without direct chemical exposure to the semiconductor material.
2Ease of manufacture
If silicon substrate is used, then substrate material is available, but silicon reacts strongly with gallium making it difficult to retain surface flatness
Solution Approach 1:
The patent introduces a silicon oxide layer as an intermediary between the silicon substrate and the gallium-containing nitride-compound semiconductor layers. This intermediary prevents direct chemical reaction between silicon and gallium, eliminating the formation of harmful reaction products that would degrade surface flatness, while still allowing the silicon substrate to be used for its mechanical and thermal properties.
3Area of stationary object
If substrate diameter is increased, then larger area is available for device fabrication, but warpage becomes more severe due to thermal expansion coefficient difference
Solution Approach 1:
The patent changes the thermal expansion parameter by forming a silicon oxide layer on the silicon substrate. The silicon oxide layer has a thermal expansion coefficient that better matches the nitride-compound semiconductor materials, reducing the thermal mismatch stress and consequently decreasing warpage in large-diameter substrates during the high-temperature growth process.
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 effectively reduces warpage and maintains substrate flatness, preventing crystalline defects and improving device yield by balancing thermal expansion coefficients and facilitating the removal of deposition substances without damaging the substrate.
Implementation Method 1
Thermal expansion coefficient of the nitride-compound semiconductor is different from that of the different kind of each substrate. Therefore, warpage is generated in the stacked nitride-compound semiconductor structure
Implementation Method 2
forming a first protection film on a second surface of a substrate... forming a first nitride-compound semiconductor layer on the first surface of the substrate
Implementation Method 3
it is necessary to remove the deposition substances on the substrate without damage to the surface of the substrate
Data Source
AI summary
According to one embodiment, a method for fabricating a stacked nitride-compound semiconductor structure includes forming a first protection film on a second surface of a substrate, forming a first nitride-compound semiconductor layer on the first surface of the substrate, forming a second protection film on the first nitride-compound semiconductor layer, removing the first protection film to expose the second surface of the substrate, forming a second nitride-compound semiconductor layer on the second surface of the substrate, and removing the second protection film to expose the first surface of the second nitride-compound semiconductor layer.