Backside Semiconductor Contact via Hydrogen Plasma Etching
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Solution Overview
Problem
Current methods for forming backside contacts in semiconductor devices, such as argon sputtering and wet etching, result in unsatisfactory cleaning due to silicon debris, carbon contamination, and fluorine introduction, leading to increased contact resistance and damage to existing metallization layers.
Innovation Solution
The use of hydrogen plasma etching to remove native oxide from the backside of semiconductor wafers, creating a smooth surface with hydrogen-terminated silicon atoms that convert to metal-terminated silicon, forming a metal silicide layer for improved mechanical and ohmic contact without degrading the front-side metallization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If argon sputtering is used to remove native oxide from the backside surface, then the oxide removal is achieved, but silicon debris and carbon contamination are introduced leading to increased contact resistance
Solution Approach 1:
The patent changes the chemical composition parameters of the plasma from argon-based to hydrogen-based, fundamentally altering the cleaning mechanism from physical sputtering to chemical etching. This parameter change eliminates the generation of silicon debris and carbon contamination while maintaining effective oxide removal capability.
Solution Approach 2:
The patent replaces the mechanical sputtering process (argon ion bombardment) with a chemical etching process (hydrogen plasma). This substitution eliminates the mechanical damage and contamination associated with sputtering while achieving the same oxide removal function through chemical reactions.
2Manufacturing precision
If wet etching is used to clean the backside surface, then oxide removal is achieved, but fluorine contaminants are introduced increasing contact resistance
Solution Approach 1:
The patent replaces wet chemical etching with plasma-based hydrogen etching. This substitution eliminates the introduction of fluorine contaminants while maintaining the oxide removal function, as hydrogen plasma etches silicon oxide without introducing halogen-based contaminants.
Solution Approach 2:
The patent uses hydrogen plasma in a controlled atmosphere that prevents the introduction of harmful contaminants. The hydrogen-based environment is inherently free from fluorine sources, eliminating the contamination problem associated with wet etching processes.
3Manufacturing precision
If aggressive cleaning methods are used to remove native oxide, then surface cleanliness is improved, but damage to existing metallization layers occurs
Solution Approach 1:
The patent changes the etching chemistry from aggressive physical sputtering to milder chemical etching using hydrogen plasma. This parameter change allows for effective oxide removal at lower energies, preventing damage to the overlying metallization layers while maintaining surface cleanliness.
Solution Approach 2:
The hydrogen plasma acts as an intermediary that selectively etches silicon oxide while being gentler on metal layers. The chemical selectivity of hydrogen plasma provides a buffering effect that protects the metallization layers from direct damage during the cleaning process.
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
Hydrogen plasma etching provides a cleaner, less damaged surface with superior adhesion and surface uniformity, reducing contact resistance and maintaining the integrity of existing metallization layers, while effectively removing carbon and fluorine contaminants.
Implementation Method 1
The workpiece is placed in a plasma etch tool chamber, and argon at a first flow rate and hydrogen at a second flow rate are introduced into the plasma etch tool chamber. The hydrogen plasma is ignited and the flow rate of hydrogen is increased to a third flow rate. The hydrogen plasma removes a native oxide from the first bottom surface to expose a second bottom surface of the workpiece.
Implementation Method 2
The use of hydrogen plasma etching to remove native oxide from the backside of semiconductor wafers, creating a smooth surface with hydrogen-terminated silicon atoms that convert to metal-terminated silicon
Implementation Method 3
A first metal layer is disposed over the metal silicide layer such that a metal of the first metal layer is the same as a metal of the metal silicide layer
Data Source
AI summary
A semiconductor device includes a workpiece having a bottom surface opposite the top surface. Metallization layers are disposed over the top surface and a protective layer is disposed over the metallization layers. The semiconductor device further includes a metal silicide layer disposed on the bottom surface. The metal silicide layer is less than about five atomic layers in thickness. A first metal layer is disposed over the metal silicide layer such that a metal of the first metal layer is the same as a metal of the metal silicide layer.