Semiconductor Substrate Doping Profile for Low-Stress Epitaxial Layers
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Solution Overview
Problem
The existing semiconductor substrate manufacturing processes face challenges in optimizing dopant distribution and substrate characteristics, leading to issues with device reliability and parameters such as wafer bow and stress, which affect the quality of semiconductor chips.
Innovation Solution
A method involving a semiconductor substrate with two dopants of different covalent atomic radii, where one dopant is introduced through the main surface and the other through both surfaces, followed by a process to form a semiconductor layer and reduce substrate thickness, ensuring a controlled vertical concentration profile to minimize wafer bow and stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single dopant is used in the semiconductor substrate, then the doping process is simple, but the stress control and lattice mismatch are insufficient
Solution Approach 1:
The doping process is segmented into two distinct steps: first doping with a dopant having a smaller covalent atomic radius, then doping with a dopant having a larger covalent atomic radius. This segmentation allows independent optimization of each dopant's concentration and distribution, enabling precise control over stress and lattice mismatch while maintaining manufacturing feasibility
Solution Approach 2:
Different regions of the semiconductor substrate are doped with different dopants having different covalent atomic radii. The first dopant (smaller radius) is used in regions requiring lattice compression, while the second dopant (larger radius) is used in regions requiring lattice expansion. This local quality differentiation enables precise control of stress distribution and lattice matching across the substrate
2Reliability
If the semiconductor substrate thickness is reduced, then the device performance is improved, but the stress and wafer bow increase
Solution Approach 1:
The patent uses dopants with opposite effects on lattice constants to counterbalance each other. The first dopant (smaller covalent atomic radius) causes lattice compression, while the second dopant (larger covalent atomic radius) causes lattice expansion. By carefully controlling the concentrations and distributions of these opposing dopants, the net stress and wafer bow are compensated, allowing substrate thinning without compromising mechanical stability
Solution Approach 2:
The patent changes multiple parameters simultaneously: the covalent atomic radii of dopants, their concentration ratios, their vertical distribution profiles, and the substrate thickness. By coordinating these parameter changes, the patent achieves a state where reduced substrate thickness does not lead to increased stress or wafer bow, but rather to improved device performance with controlled mechanical properties
3Reliability
If dopant concentration is increased to reduce resistivity, then the electrical conductivity is improved, but the stress and lattice mismatch worsen
Solution Approach 1:
The patent applies different dopants with different covalent atomic radii to different regions or layers of the semiconductor substrate. The first dopant (smaller radius) is used where lattice compression is beneficial, while the second dopant (larger radius) is used where lattice expansion is needed. This spatial differentiation allows high overall dopant concentration for low resistivity while maintaining local lattice stability and minimizing stress
Solution Approach 2:
The semiconductor substrate is created as a composite doped structure containing two different dopants with complementary properties. This composite doping approach allows the substrate to simultaneously achieve high electrical conductivity (through high total dopant concentration) and low stress (through balanced distribution of dopants with opposing lattice effects)
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 enhances the characteristics of semiconductor substrates by reducing overall stress and lattice mismatch, resulting in low-resistive and high-conductive substrates with improved device manufacturing outcomes.
Implementation Method 1
a vertical concentration profile N1(y) of the first dopant decreases along at least 80% of a distance between an interface of the semiconductor substrate and the semiconductor layer to a surface of the semiconductor substrate opposite to the interface
Implementation Method 2
forming a semiconductor layer on the first main surface
Data Source
AI summary
A semiconductor device includes a semiconductor substrate having a first dopant and a second dopant. A covalent atomic radius of a material of the semiconductor substrate is i) larger than a covalent atomic radius of the first dopant and smaller than a covalent atomic radius of the second dopant, or ii) smaller than the covalent atomic radius of the first dopant and larger than the covalent atomic radius of the second dopant. The semiconductor device further includes a semiconductor layer on the semiconductor substrate and semiconductor device elements in the semiconductor layer. A vertical concentration profile of the first dopant decreases along at least 80% of a distance between an interface of the semiconductor substrate and the semiconductor layer to a surface of the semiconductor substrate opposite to the interface.