Thin Oxide Mask for Bipolar Transistor Buried Layer Formation
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Solution Overview
Problem
Conventional buried layer fabrication techniques in bipolar transistors result in significant silicon recess formation, which hampers the formation of shallow trench isolation regions and leads to issues like GOI failure and nitride residue blocking, limiting the integration of power processes.
Innovation Solution
Employing a thin oxide mask instead of a thick oxide mask during the drive-in process for buried layer formation, which reduces silicon recess formation and enables the integration of shallow trench isolation regions by minimizing the recess depth and preventing nitride residue issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a thick oxide mask is used during buried layer formation, then the dopant implantation is effective, but significant silicon recess formation occurs which hampers shallow trench isolation region formation
Solution Approach 1:
The patent changes the oxide mask thickness parameter from conventional thick oxide (e.g., 500-1000 nm) to thin oxide (e.g., 50-200 nm). This parameter change reduces the silicon recess depth during drive-in diffusion while maintaining adequate dopant implantation effectiveness, thereby enabling subsequent shallow trench isolation region formation without GOI failure or nitride residue blocking issues
Solution Approach 2:
The patent applies partial action by using only the minimum necessary oxide thickness to protect during implantation, rather than excessive thick oxide that causes problematic recess formation. The thin oxide provides sufficient mask protection for dopant implantation while limiting the depth of silicon recess during the drive-in process, enabling STI integration
2Reliability
If a thick oxide mask is used during drive-in process, then dopant protection is maintained, but silicon recess depth increases causing nitride residue blocking and GOI failure
Solution Approach 1:
The patent optimizes the oxide mask thickness parameter to a thin regime (50-200 nm) that provides adequate dopant protection during implantation while minimizing silicon recess depth during drive-in. This prevents the formation conditions that lead to nitride residue blocking and GOI failure, eliminating these harmful effects
3Productivity
If conventional thick oxide mask technique is used, then buried layer implantation is achieved, but silicon recess formation limits isolation region types
Solution Approach 1:
The patent changes the oxide mask thickness parameter to thin oxide (50-200 nm), which maintains buried layer implantation efficiency while reducing silicon recess depth. This enables the use of shallow trench isolation regions and other isolation structures that are incompatible with deep recesses, significantly increasing isolation region type selection and process versatility
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 use of a thin oxide mask mitigates silicon recess formation, allowing for the successful integration of shallow trench isolation regions and reducing variations in STI step height across the wafer, thereby enhancing the fabrication of bipolar junction devices and BiCMOS technology.
Implementation Method 1
The oxide layer is patterned to form an opening that exposes a portion of the semiconductor substrate
Implementation Method 2
The oxide layer is patterned to form an opening that exposes a portion of the semiconductor substrate
Implementation Method 3
Dopants are implanted into the semiconductor substrate through the opening to form a buried layer
Implementation Method 4
A buried layer diffusion process is performed to drive in the implanted dopants
Implementation Method 5
Employing a thin oxide mask instead of a thick oxide mask during the drive-in process for buried layer formation, which reduces silicon recess formation
Data Source
AI summary
A method for forming a bipolar transistor device includes providing a semiconductor substrate. An oxide layer is formed on the semiconductor substrate. The oxide layer is patterned to form an opening that exposes a portion of the semiconductor substrate. A dopant, such as antimony, is implanted into the semiconductor substrate through the opening to form a buried layer. An upper portion of the mask layer is removed to define a thin mask layer. A buried layer diffusion process is performed to drive in the implanted dopants while mitigating recess formation.