Conformal Boron Doping of 3D Semiconductor Structures
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Solution Overview
Problem
Existing methods for boron doping in semiconductor materials, particularly for p-type contact applications and three-dimensional structures like FINFETs, face challenges in achieving high concentration doping and conformality, as they are often limited to line-of-sight and fail to provide sufficient control over layer thickness, surface characteristics, and thermal budget.
Innovation Solution
A method involving the deposition of a conformal buffer layer followed by a high concentration boron layer on a semiconductor substrate, which is then annealed to diffuse boron atoms into the semiconductor material, allowing for conformal doping of three-dimensional structures without a vacuum break, thereby achieving high boron concentrations and reduced resistivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional implantation methods are used for boron doping, then the doping process is simple to implement, but the conformality on three-dimensional structures is insufficient and line-of-sight limitations occur
Solution Approach 1:
The doping process is segmented into multiple sequential steps: depositing a conformal buffer layer, depositing a conformal high concentration boron layer, annealing to diffuse boron atoms, then selectively removing the boron layer and buffer layer. This segmentation enables conformal doping of three-dimensional structures by eliminating line-of-sight limitations while maintaining process control through distinct, manageable steps.
Solution Approach 2:
A conformal buffer layer is deposited on the semiconductor surface before depositing the boron layer. This preliminary action protects the semiconductor surface, enables conformal coverage of three-dimensional structures, and serves as a foundation for subsequent selective removal processes that achieve high conformality without line-of-sight constraints.
2Reliability
If high concentration boron doping is achieved, then the resistivity of semiconductor material is lowered, but the control over layer thickness and surface characteristics becomes more difficult
Solution Approach 1:
A conformal buffer layer acts as an intermediary between the semiconductor surface and the high concentration boron layer. This intermediary enables precise control of layer thickness and surface characteristics by providing a controlled interface that facilitates uniform boron diffusion while protecting the underlying semiconductor structure during the high concentration doping process.
Solution Approach 2:
The process utilizes parameter changes including annealing temperature control (less than or equal to 800° C.) and sequential layer removal to achieve high boron concentration doping with precise thickness control. By controlling the annealing parameters and using selective etching, the method achieves both high dopant concentration and precise layer thickness management.
3Manufacturing precision
If conformal buffering layer and high concentration boron layer are deposited and annealed, then high boron concentration doping is achieved, but the process requires multiple steps increasing manufacturing complexity
Solution Approach 1:
The method maintains continuous vacuum conditions throughout the entire multi-step process, eliminating vacuum breaks between depositing the buffer layer, depositing the boron layer, annealing, and selective removal steps. This continuity of useful action enables high boron concentration control while improving processing efficiency by avoiding repeated vacuum chamber cycling and maintaining a streamlined manufacturing flow.
4Quantity of substance
If annealing is performed at high temperature to diffuse boron atoms, then the doping concentration is increased, but the thermal budget increases affecting other process steps
Solution Approach 1:
The process achieves high boron doping concentration by controlling annealing temperature at less than or equal to 800° C., which is lower than conventional high-temperature annealing. This parameter change, combined with the conformal buffer layer structure and selective removal process, enables achieving the required boron concentration (greater than or equal to 2×10^20 atoms/cm³) while maintaining a constrained thermal budget that is compatible with other process steps.
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 method enables conformal doping of semiconductor materials with boron concentrations greater than 2×10^20 atoms/cm3, effectively lowering resistivity and maintaining the structural integrity of three-dimensional structures, while allowing for efficient processing without the need for frequent vacuum breaks, thus enhancing substrate throughput and reducing operational costs.
Implementation Method 1
The substrate is annealed to diffuse boron atoms from the high concentration boron layer, through the buffer layer, into the semiconductor material
Implementation Method 2
The high concentration boron layer is removed from the substrate by a selective etch process which utilizes the buffer layer as an etch stop layer
Implementation Method 3
The buffer layer is removed from the substrate by a selective etch process which utilizes the semiconductor material as an etch stop layer
Data Source
AI summary
Methods of doping a semiconductor material are disclosed. Some embodiments provide for conformal doping of three dimensional structures. Some embodiments provide for doping with high concentrations of boron for p-type doping.