Nitride Semiconductor Substrate Separation via Sacrificial Layer
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Solution Overview
Problem
The manufacturing of nitride semiconductor devices faces challenges due to the lack of lattice-constant-matched substrates, leading to performance degradation and complex, costly substrate separation processes, particularly with sapphire substrates which have low thermal conductivity.
Innovation Solution
A method involving sequential epitaxial layer stacking, trench formation, and sacrificial layer use to separate semiconductor layers from a substrate, utilizing a sacrificial layer with a different lattice constant and applying stress to induce crack propagation for partial spalling and thickness adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sapphire substrate is used for nitride semiconductor device manufacturing, then the device can be formed on a substrate, but the low thermal conductivity of the sapphire substrate causes degradation of device performance
Solution Approach 1:
The patent segments the substrate system by introducing a sacrificial layer between the sapphire substrate and the nitride semiconductor layers. This allows the semiconductor structure to be separated from the sapphire substrate after growth, enabling transfer to a different host substrate with better thermal conductivity properties.
Solution Approach 2:
The sacrificial layer acts as an intermediary that facilitates the separation process. It is positioned between the sapphire substrate and the nitride semiconductor layers, allowing controlled delamination through crack propagation when stress is applied, thereby enabling substrate transfer without direct bonding between semiconductor and sapphire.
2Adaptability or versatility
If a sapphire substrate is removed from the nitride semiconductor device, then the device can be transferred to a host substrate with desirable characteristics, but expensive processing equipment such as laser lift-off equipment is required or the yield is degraded due to the complexity of the substrate separating process
Solution Approach 1:
The sacrificial layer is pre-formed during the epitaxial growth process before device fabrication. This preliminary preparation enables subsequent simple mechanical or chemical separation methods to be used, avoiding the need for expensive laser lift-off equipment while maintaining high yield.
Solution Approach 2:
The patent changes the physical and chemical parameters of the interface between the sapphire substrate and the nitride semiconductor layers by introducing the sacrificial layer with different lattice constant and bonding characteristics. This enables controlled separation through crack propagation at specific stress conditions, simplifying the substrate removal process.
3Adaptability or versatility
If the nitride semiconductor layers are separated from the sapphire substrate, then the device can be transferred to a host substrate, but the separation process requires complex equipment or reduces manufacturing yield
Solution Approach 1:
The sacrificial layer is formed in advance during the standard epitaxial growth process, creating a pre-defined separation plane. This preliminary action ensures that subsequent separation can be performed using simple, low-cost methods without compromising manufacturing yield.
Solution Approach 2:
The sacrificial layer is designed as a temporary, disposable component that is removed after serving its separation function. This allows the use of inexpensive separation methods while achieving high-yield substrate transfer to host substrates.
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
Enables efficient separation of semiconductor device parts with reduced complexity and cost, maintaining device performance by adjusting thickness and using a flexible substrate for improved thermal and mechanical characteristics.
Implementation Method 1
the sacrificial layer may have a lattice constant different from lattice constants of the first epitaxial layer and the second epitaxial layer
Implementation Method 2
Propagation of a crack may start, due to the stress, at one end of the sacrificial layer which contacts the metal film. The crack may progress along the sacrificial layer.
Implementation Method 3
sequentially stacking a first epitaxial layer, a sacrificial layer, a second epitaxial layer, and a third epitaxial layer on a first substrate
Data Source
AI summary
A semiconductor device includes a first semiconductor layer. A second semiconductor layer is disposed on the first semiconductor layer. A structure layer is disposed on the second semiconductor layer. A metal film covers a side surface of the first semiconductor layer, a side surface of the second semiconductor layer, and an upper surface of the structure layer. A flexible substrate covers the metal film.