Carbon-Diffused Nitride Semiconductor Substrate for Warp Suppression
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Solution Overview
Problem
High-frequency devices using silicon single crystal substrates with high resistivity and low oxygen content are prone to plastic deformation during epitaxial growth and device processes, leading to warp abnormalities and bonding failures.
Innovation Solution
A nitride semiconductor substrate is produced using a silicon single crystal substrate with a carbon diffusion layer implanted by RTA, having a carbon concentration of 5E+16 atoms/cm3 or more, and an Al layer formed as an intermediate layer to improve adhesiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high resistivity silicon single crystal substrate with low oxygen is used, then parasitic capacitance is reduced and high-frequency characteristics are improved, but the substrate becomes more prone to plastic deformation during epitaxial growth
Solution Approach 1:
The patent applies local quality by forming a carbon diffusion layer only in the surface regions (front and back surfaces) of the silicon substrate, while maintaining the bulk substrate properties (high resistivity, low oxygen) unchanged. This localized carbon doping reinforces the surface regions to resist plastic deformation during epitaxial growth, while the bulk substrate retains its low parasitic capacitance characteristics for high-frequency operation.
Solution Approach 2:
The patent creates a composite structure by combining carbon-diffused surface layers with the bulk silicon substrate. The carbon diffusion layer (with carbon concentration of 1E+19 to 1E+21 atoms/cm³) forms a composite material system where the carbon-enriched surface regions provide enhanced mechanical strength and deformation resistance, while the underlying bulk silicon maintains the electrical properties necessary for high-frequency device operation.
2Manufacturing precision
If stress relaxation is performed by using a complex intermediate layer of gallium nitride based compound semiconductors, then warps and cracks are reduced, but production time increases and design freedom is reduced
Solution Approach 1:
The patent extracts the stress relaxation function from the complex multi-layer gallium nitride intermediate structure and relocates it to the silicon substrate itself through carbon diffusion. By modifying the silicon substrate's surface regions with carbon, the substrate gains inherent stress resistance capability, eliminating the need for additional intermediate layers and thereby reducing production steps and time.
Solution Approach 2:
The carbon diffusion layer acts as an intermediary that mediates between the silicon substrate and the epitaxial growth process. This carbon-enriched surface layer serves as a buffer that absorbs and distributes thermal and mechanical stresses during epitaxial growth, preventing warp and crack formation without requiring complex intermediate semiconductor layers.
3Strength
If carbon doping is performed in the bulk crystal stage by RTA, then high-strength silicon single crystal wafers are obtained, but controlled carbon concentration is difficult to achieve and yield decreases
Solution Approach 1:
The patent applies partial action by performing carbon diffusion only in the surface regions (front and back surfaces) of the silicon substrate rather than throughout the entire bulk crystal. This localized diffusion approach, achieved through RTA processing, allows precise control of carbon concentration (1E+19 to 1E+21 atoms/cm³) in the surface layers while leaving the bulk substrate unchanged, thereby achieving both high mechanical strength and controlled carbon concentration.
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
The carbon diffusion layer effectively suppresses plastic deformation and warp failures during epitaxial growth, while the Al layer enhances the adhesiveness of the nitride semiconductor thin film, resulting in a stable and reliable nitride semiconductor substrate.
Implementation Method 1
the silicon single crystal substrate has a carbon diffusion layer which has been implanted with carbon and has a carbon concentration higher than a bulk portion of the silicon single crystal substrate
Implementation Method 2
A nitride semiconductor substrate is produced using a silicon single crystal substrate with a carbon diffusion layer implanted by RTA
Implementation Method 3
an Al layer formed as an intermediate layer to improve adhesiveness
Implementation Method 4
a nitride semiconductor thin film formed on the front surface
Data Source
AI summary
A nitride semiconductor substrate includes: a silicon single crystal substrate having a front surface and a back surface; and a nitride semiconductor thin film formed on the front surface, in which the silicon single crystal substrate has a carbon diffusion layer that has been implanted with carbon and has a carbon concentration higher than a bulk portion of the silicon single crystal substrate in at least the front surface and the back surface, and the carbon concentration in the carbon diffusion layer is 5E+16 atoms/cm3 or more. The nitride semiconductor substrate can suppress warp failure caused by plastic deformation during epitaxial growth and device processes when the nitride semiconductor substrate is produced using a silicon single crystal substrate.