Haloborane Epitaxy for High-Boron Selective pMOS Growth
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Solution Overview
Problem
Conventional epitaxial deposition methods for pMOS films using diborane as a boron source suffer from low selectivity and boron concentration limitations, leading to poor crystalline film growth and boron-rich layer formation on dielectric areas, especially at high concentrations.
Innovation Solution
Employing haloboranes, such as BCl3, as a boron-containing gas in combination with Group IV element-containing gases, and using etchants like HCl to selectively grow boron-containing structures on crystalline surfaces while passivating dielectric surfaces, achieving boron concentrations above 3×1020 atoms/cm3.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If diborane (B2H6) is used as boron source at high concentrations to achieve higher boron doping levels, then boron concentration in film increases, but selectivity deteriorates and boron-rich non-epitaxial layers form on dielectric areas
Solution Approach 1:
The patent changes the chemical parameters of the boron source gas from diborane (B2H6) to haloboranes (such as BCl3, BBr3, or BI3). This parameter change fundamentally alters the decomposition behavior and reactivity of the boron source, enabling high boron concentrations (>3×10^20 atoms/cm³) to be achieved without the selectivity loss and non-epitaxial layer formation that occur with diborane at similar concentrations.
2Quantity of substance
If diborane (B2H6) is used as boron source, then boron deposition occurs, but thermal decomposition leads to poor selectivity and crystalline film degradation
Solution Approach 1:
The patent changes the chemical composition parameter of the boron source from diborane to haloboranes. Haloboranes have different thermal stability characteristics and decomposition pathways compared to diborane, allowing boron deposition to proceed without the excessive decomposition that degrades crystalline film quality and reduces selectivity.
3Reliability
If higher etchant amounts are used to maintain selectivity at high boron concentrations, then selectivity is improved, but process complexity and potential film damage increase
Solution Approach 1:
The patent changes the boron source gas parameter to haloboranes, which inherently provide better selectivity at high boron concentrations without requiring proportionally higher etchant amounts. This parameter change reduces the need for aggressive etching, thereby simplifying the overall process and reducing potential film damage from excessive etchant exposure.
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
Enhances selectivity and growth rates, preventing boron-rich layer formation on dielectric areas and improving pMOS film crystallinity, enabling higher boron concentrations and better film quality.
Implementation Method 1
B2H6 decomposes easily upon thermal heating
Implementation Method 2
Selective epitaxial deposition of, e.g., silicon (Si)
Data Source
AI summary
Embodiments of the present invention generally relate to methods of epitaxially growing boron-containing structures. In an embodiment, a method of depositing a structure comprising boron and a Group IV element on a substrate is provided. The method includes heating the substrate at a temperature of about 300° C. or more within a chamber, the substrate having a dielectric material and a single crystal formed thereon. The method further includes flowing a first process gas and a second process gas into the chamber, wherein: the first process gas comprises at least one boron-containing gas comprising a haloborane; and the second process gas comprises at least one Group IV element-containing gas. The method further includes exposing the substrate to the first and second process gases to epitaxially and selectively deposit the structure comprising boron and the Group IV element on the single crystal.