Epitaxial Layer Ion Containment in Semiconductor Fabrication
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
As semiconductor devices become more highly integrated, the ions implanted during the halo ion implantation process tend to diffuse into the channel region, negatively impacting transistor performance by increasing threshold voltage and reducing charge carrier mobility due to smaller critical dimensions.
Innovation Solution
A method involving pre-halo ion implantation followed by epitaxial growth of a first and second layer, where the first epitaxial layer prevents ions from diffusing into the second epitaxial layer, thereby forming a semiconductor device with improved ion containment and reduced short channel effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If halo ion implantation is performed to suppress short channel effects, then transistor performance is improved, but ions diffuse into the channel region causing threshold voltage increase and reduced charge carrier mobility
Solution Approach 1:
An epitaxial layer is introduced as an intermediary barrier between the substrate and the channel region. This layer physically blocks the diffusion path of ions, preventing them from reaching the channel region while still allowing the halo implantation to occur in the substrate. The epitaxial layer acts as a protective mediator that separates the ion source from the sensitive channel area.
Solution Approach 2:
The semiconductor structure is segmented into distinct layers: the substrate, the epitaxial layer, and the channel region. This segmentation creates a physical barrier that confines ions to specific regions. The epitaxial layer is grown to a sufficient thickness to stop ion diffusion, effectively segmenting the device structure to prevent harmful ion migration while maintaining electrical functionality.
2Productivity
If critical dimension of gate region is reduced to increase integration density, then device integration is improved, but ion diffusion into channel region is enhanced causing increased threshold voltage distribution
Solution Approach 1:
The epitaxial layer serves as a mediator that decouples the relationship between critical dimension reduction and ion diffusion. By introducing this intermediate layer, the system allows for smaller gate dimensions to achieve higher integration while the epitaxial layer maintains control over ion distribution, preventing excessive threshold voltage variations even as device dimensions scale down.
Solution Approach 2:
The epitaxial layer is formed in advance before the halo ion implantation process. This preliminary action creates a pre-established barrier that controls subsequent ion diffusion. By preparing this protective layer beforehand, the process ensures that when ions are implanted, their diffusion is already constrained, preventing threshold voltage distribution issues that would otherwise arise from direct ion exposure to the channel region.
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
The approach effectively prevents ion diffusion into the channel region, maintaining transistor performance and reliability by minimizing threshold voltage alterations and charge carrier mobility reduction.
Implementation Method 1
epitaxially growing a layer of material on the entirety of an upper surface of the semiconductor substrate to thereby form a first epitaxial layer
Implementation Method 2
implanting ions into a semiconductor substrate in a pre-halo ion implantation process
Data Source
AI summary
A method of fabricating a semiconductor device includes performing pre-halo ion implantation on a semiconductor substrate, forming a first epitaxial layer over the entire upper surface of the semiconductor substrate, forming a second epitaxial layer over the entire surface of the first epitaxial layer, and forming a transistor at an active region of the second epitaxial layer. The first epitaxial layer prevents the ions implanted in the semiconductor substrate in the pre-halo implantation process from diffused into the second epitaxial layer under the effects of a process used to form the transistor.