Laser-Induced Liquid Phase Doping for Shallow Junctions
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Solution Overview
Problem
Current doping processes for semiconductors, particularly Germanium-based, face issues such as damage recovery requirements, contamination risks, limited dopant sensitivity, out-diffusion phenomena, and inability to create shallow or ultra-shallow junctions, which are not compatible with all semiconductor materials and applications.
Innovation Solution
A p+ or n+ type doping process involving the deposition of a thin dopant source layer and a protective surface layer, followed by laser-induced liquefaction and controlled cooling to achieve dopant diffusion and crystalline regrowth, avoiding high-temperature processing and contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If ion implantation is used for doping, then dopant can be introduced into the semiconductor, but damage is induced requiring subsequent annealing treatment
Solution Approach 1:
The patent replaces the mechanical ion implantation process with a chemical deposition process followed by laser-induced liquid phase doping. Instead of physically bombarding the semiconductor with ions, the dopant is introduced through deposition of a dopant-containing layer that is then activated by laser heating, eliminating mechanical damage to the crystal structure.
Solution Approach 2:
The patent utilizes phase transitions of the dopant layer through laser-induced heating to melt and then rapidly cool the layer, creating a liquid phase that enables dopant diffusion into the semiconductor substrate without requiring high-temperature annealing that could cause damage.
2Reliability
If high temperature processing is used for annealing or diffusion, then dopant activation is achieved, but contamination risk increases
Solution Approach 1:
The patent changes the temperature parameter profile by using rapid laser heating followed by rapid cooling, achieving dopant activation through a brief, localized temperature spike rather than prolonged high-temperature processing. This minimizes the time window for contamination while maintaining effective dopant activation.
Solution Approach 2:
The patent substitutes thermal diffusion processes with laser-induced liquid phase doping, where the dopant is introduced during the liquid phase formation and solidification process rather than through high-temperature diffusion, thereby avoiding contamination associated with high-temperature processing.
3Quantity of substance
If conventional doping processes are used, then doping is achieved, but out-diffusion phenomena occur reducing precision
Solution Approach 1:
The patent employs a pulsed laser approach where the laser is applied in controlled pulses to the dopant layer, creating periodic heating cycles that precisely control the timing and extent of dopant diffusion. The pulsed nature allows for exact control of diffusion depth by adjusting pulse duration and intensity.
Solution Approach 2:
The patent utilizes the phase transition of the dopant layer from solid to liquid and back to solid through controlled laser heating and cooling. The dopant diffuses primarily during the liquid phase, and the rapid solidification freezes the dopant distribution at the desired depth, preventing out-diffusion and achieving precise depth control.
4Quantity of substance
If standard doping techniques are used, then doping is achieved, but shallow and ultra-shallow junctions cannot be implemented
Solution Approach 1:
The patent exploits the liquid phase of the dopant layer created by laser heating to enable dopant diffusion at very shallow depths. The rapid heating and cooling cycle confines the diffusion process to a thin region near the surface, making it possible to create shallow and ultra-shallow junctions that cannot be achieved with conventional diffusion processes.
Solution Approach 2:
The patent applies only a portion of the dopant layer to the semiconductor surface through controlled deposition, and the laser processing activates only the deposited dopant. By controlling the deposition amount and laser parameters, the process achieves precise control over dopant concentration and junction depth, enabling shallow junction formation.
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 process enables highly doped surface layers with reduced dopant out-diffusion, cost-effective compared to ion implantation, and allows for varied dopant concentration and thickness, facilitating shallow junctions suitable for micro/nano-electronics applications.
Implementation Method 1
inducing liquefaction of the surface layer at least until the source layer by emitting on the substrate surface one or more laser pulses
Implementation Method 2
inducing liquefaction of the surface layer at least until the source layer
Implementation Method 3
obtain the diffusion of the dopant material
Implementation Method 4
cooling down the substrate surface, so as to obtain solidification of the semiconductor material of the surface layer
Data Source
Figure 1~1b
Figure 2~3
Figure 4~5
AI summary
A p+ or n+ type doping process for semiconductors, allows to implement a semiconductor with a highly doped surface layer, and it comprises the steps of: providing a substrate made of semiconductor material; depositing on a surface of 5 the substrate made of semiconductor material a thin source layer made of dopant material acting as dopant source; depositing on said source layer an additional protective surface layer made of semiconductor material; inducing liquefaction of the surface layer at least until the source layer; and cooling down the substrate surface so as to obtain the diffusion of the dopant material.