Plasma-Assisted Germanium Doping for Ultra-Shallow Junctions
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Solution Overview
Problem
Current ion implantation processes, such as ion implantation (I2P), face challenges in forming ultra-shallow junctions in germanium substrates due to high energy usage and subsequent ion diffusion during annealing, making it difficult to achieve junctions less than 10 nanometers in depth.
Innovation Solution
A method involving plasma-assisted doping using a mixture of phosphorous and antimony gas species in a substrate processing chamber, including pretreatment with hydrogen plasma, controlled pressure, and flash annealing to form an ultra-shallow junction in the germanium layer, with the option of sequential or simultaneous doping and varying gas concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If ion implantation is used to dope germanium, then dopant concentration can be increased, but junction depth becomes too deep (greater than 10 nm) due to high energy and subsequent diffusion during annealing
Solution Approach 1:
The patent changes the physical state of the dopant delivery from solid/ion form to gaseous plasma form. This allows dopants to be delivered at lower energies through plasma deposition and in-situ annealing, enabling precise control of junction depth while maintaining high dopant concentration in the germanium substrate
Solution Approach 2:
The patent replaces the mechanical ion implantation process with a plasma-based chemical deposition process. Instead of physically accelerating ions into the substrate, dopants are delivered via plasma species that deposit and activate at lower energies, eliminating the diffusion problem caused by high-energy implantation
2Quantity of substance
If high energy ion implantation is used, then dopant can be introduced into germanium, but thermal diffusion during annealing causes dopants to spread beyond the desired ultra-shallow junction depth
Solution Approach 1:
The patent performs annealing at low temperatures (below 200°C) using in-situ plasma, which provides the necessary thermal energy for dopant activation and electrical functionality while being insufficient to cause significant thermal diffusion. This temperature parameter control prevents dopant spreading while achieving the desired electrical characteristics
Solution Approach 2:
The patent uses plasma as an intermediary medium that delivers both dopant species and activation energy simultaneously. The plasma provides reactive species that facilitate dopant incorporation and electrical activation without requiring high-temperature thermal processes that would cause diffusion
3Quantity of substance
If conventional plasma doping is used, then dopant can be deposited, but dopant concentration and uniformity are insufficient for ultra-shallow junction formation
Solution Approach 1:
The patent performs a preliminary plasma treatment of the germanium substrate surface before dopant deposition. This pre-treatment step prepares the surface by cleaning and activating it, creating optimal conditions for subsequent dopant deposition and ensuring uniform, controlled incorporation at the desired ultra-shallow depths
Solution Approach 2:
The patent employs real-time monitoring and control of plasma parameters (power, pressure, gas flow) during the doping process. This feedback control ensures consistent dopant delivery rates and plasma conditions, achieving the precise concentration and depth control required for ultra-shallow junctions
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 effectively creates ultra-shallow junctions with depths less than 10 nanometers by suppressing dopant diffusion and enhancing phosphorous concentration, allowing for precise control of junction formation and minimizing thermal impact on the substrate.
Implementation Method 1
striking plasma in the processing chamber for a predetermined doping period
Implementation Method 2
performing a plasma pretreatment on the substrate in the processing chamber for a predetermined pretreatment period using a pretreatment plasma gas mixture including hydrogen gas species
Implementation Method 3
annealing the substrate during a predetermined annealing period to form the junction in the germanium (Ge) layer
Data Source
AI summary
A method for forming a junction in a germanium (Ge) layer of a substrate includes arranging the substrate in a processing chamber. The method includes performing a plasma pretreatment on the substrate in the processing chamber for a predetermined pretreatment period using a pretreatment plasma gas mixture including hydrogen gas species. The method includes supplying a doping plasma gas mixture to the processing chamber including a phosphorous (P) gas species and an antimony (Sb) gas species. The method includes striking plasma in the processing chamber for a predetermined doping period. The method includes annealing the substrate during a predetermined annealing period to form the junction in the germanium (Ge) layer.