Shallow Junction Formation via Molecular Ion Beam Amorphization
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Solution Overview
Problem
The challenge in semiconductor manufacturing is to form ultra-shallow, abrupt junctions in CMOS devices, where existing methods face issues with dopant diffusion and end-of-range defects due to transient enhanced diffusion, requiring innovative approaches to achieve precise doping profiles and minimize junction depth.
Innovation Solution
The technique involves generating an ion beam from molecular ions such as digermane, germanium nitride, or germanium-fluorine compounds to pre-amorphize semiconductor wafers, followed by co-implanting carbon or fluorine species to mitigate dopant diffusion, using low-temperature ion implantation and combining these steps with rapid thermal anneal processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pre-amorphization implant process is used to create an abrupt, ultra-shallow junction, then a relatively thick amorphous silicon layer is preferred to prevent channeling and reduce end-of-range defects, but this results in a deeper junction depth and less abrupt doping profile
Solution Approach 1:
The patent changes the physical state and composition parameters by introducing a thin amorphous silicon layer (contrary to the conventional thick layer) and co-implanting carbon species to modify the material properties. This allows achieving abrupt junctions with reduced depth by altering the interaction between dopant ions and the silicon lattice through carbon-mediated mechanisms that suppress channeling and end-of-range defects without requiring a thick amorphous layer
Solution Approach 2:
Carbon species are introduced as an intermediary element that mediates the interaction between dopant ions and the silicon crystal lattice. The carbon atoms suppress channeling effects and reduce end-of-range defects by modifying the stopping power and scattering characteristics of the implantation process, enabling shallower and more abrupt junctions than conventional silicon-only pre-amorphization can achieve
2Manufacturing precision
If conventional ion implantation is used for doping, then dopant atoms can be implanted into the substrate, but transient enhanced diffusion causes dopants to diffuse deeper into the wafer beyond the desired junction depth
Solution Approach 1:
The patent applies preliminary anti-action by co-implanting carbon species before or during the dopant implantation process. The carbon atoms create a barrier that prevents transient enhanced diffusion by reducing the mobility of dopant atoms in the damaged region, thereby counteracting the harmful diffusion effect before it can significantly increase junction depth
Solution Approach 2:
The patent creates a composite structure in the implantation region by introducing carbon species alongside dopant atoms. This carbon-dopant-silicon composite system exhibits modified diffusion characteristics where the carbon component suppresses the transient enhanced diffusion of dopants, enabling precise control over doping profiles and junction depths
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 effectively reduces dopant diffusion and enhances the formation of shallow, abrupt junctions by controlling the amorphization and co-implantation processes, improving the activation and confinement of dopants within the desired surface region, thus addressing the limitations of existing techniques.
Implementation Method 1
causing the ion beam to impact a semiconductor wafer to amorphize at least one portion of the semiconductor wafer
Implementation Method 2
Ion implantation is a process of depositing chemical species into a substrate by direct bombardment of the substrate with energized ions
Data Source
AI summary
Techniques for forming shallow junctions are disclosed. In one particular exemplary embodiment, the techniques may be realized as a method for forming shallow junctions. The method may comprise generating an ion beam comprising molecular ions based on one or more materials selected from a group consisting of: digermane (Ge2H6), germanium nitride (Ge3N4), germanium-fluorine compounds (GFn, wherein n=1, 2, or 3), and other germanium-containing compounds. The method may also comprise causing the ion beam to impact a semiconductor wafer.