Self-Aligned Dopants in Semiconductor Fins via BSG and PSG Layers
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Solution Overview
Problem
Conventional doping methods for semiconductor fins in finFETs result in damaged borosilicate glass layers and unwanted dopant interaction, leading to weak points and dopants entering shallow trench isolation regions.
Innovation Solution
A method involving the formation of self-aligned dopant layers using borosilicate glass and phosphosilicate glass layers with silicon nitride capping layers, ensuring dopants are driven into fins without entering STI regions, by carefully depositing and etching these layers to prevent interaction and damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional doping methods are used to introduce dopants into semiconductor fins, then dopants can be introduced into the fins, but the BSG layer gets damaged and dopants enter STI regions causing unwanted doping
Solution Approach 1:
The substrate is divided into first and second portions with different doping configurations. The first portion receives both BSG and PSG layers for self-aligned doping, while the second portion receives only BSG layer. This segmentation allows comparison and validation of the self-aligned doping approach while maintaining conventional doping in other regions.
Solution Approach 2:
A mask layer is introduced as an intermediary element to selectively protect the BSG layer on the first portion during etching operations. The mask layer enables precise control over where the PSG layer is removed, ensuring that dopants are introduced only in desired fin regions without damaging the BSG layer or entering STI regions.
2Quantity of substance
If dopants are driven into fins using conventional methods, then doping is achieved, but dopants also enter STI regions between fins causing unwanted doping
Solution Approach 1:
The BSG layer is formed on the fins before the PSG layer is deposited and subsequently removed from the first portion. This preliminary formation of the BSG layer with its dopant source establishes a self-aligned configuration that prevents dopants from entering STI regions during subsequent doping operations, as the BSG layer acts as a barrier in those areas.
Solution Approach 2:
Different regions of the substrate receive different layer configurations: the first portion has both BSG and PSG layers for self-aligned doping that prevents STI contamination, while the second portion has only BSG layer for conventional doping. This local differentiation allows targeted control over dopant distribution and prevents unwanted doping in STI regions where applicable.
3Adaptability or versatility
If PSG layer is removed by etching from p-FETs, then selective doping is achieved, but the BSG layer gets damaged
Solution Approach 1:
A mask layer is deposited over the PSG layer on the first portion of the substrate as an intermediary protective element. During etching operations, this mask layer protects the underlying BSG layer from damage while allowing selective removal of PSG in specific regions. The mask layer enables the etching process to proceed without compromising BSG layer integrity, thus maintaining both selective doping capability and BSG layer reliability.
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 self-aligned dopant introduction in semiconductor fins without damaging the borosilicate glass layer and reduces unwanted dopant interaction, maintaining the integrity of the semiconductor device.
Implementation Method 1
forming a first silicon nitride (SiN) layer on the BSG layer; forming a second SiN layer over the high quality oxide layer and the PSG layer
Implementation Method 2
removing the SiN material and the BSG material from the second portion of the substrate and from the semiconductor fins on the second portion of the substrate
Data Source
AI summary
A method of introducing self-aligned dopants in semiconductor fins and the resulting device are provided. Embodiments include providing semiconductor fins on first and second portions of a substrate; forming a BSG layer on side surfaces of the semiconductor fins on the first portion of the substrate; forming a first SiN layer on the BSG layer; forming a high quality oxide layer over an upper surface of the substrate, the first SiN layer and side surfaces of the semiconductor fins on the second portion of the substrate; forming a PSG layer over the high quality oxide layer on the second portion of the substrate and side surfaces of the semiconductor fins on the second portion of the substrate; and forming a second SiN layer over the high quality oxide layer and the PSG layer.