Retrograde Doped Channel for Row Hammer Leakage Suppression
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Solution Overview
Problem
Highly integrated semiconductor memory devices are vulnerable to the 'row hammer' phenomenon, where repeated operation of a word line can lead to data loss in adjacent cells due to leakage, compromising security and data integrity.
Innovation Solution
The semiconductor device incorporates a buried word line with a retrograde doping profile and a well ion implantation region, along with counter ion implantation, to enhance the channel's doping concentration and reduce leakage, thereby improving resistance to the row hammer effect without altering threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional doping profile is used in highly integrated semiconductor memory devices, then manufacturing is simpler, but the device becomes vulnerable to row hammer phenomenon causing data loss due to leakage
Solution Approach 1:
The patent applies parameter changes by implementing a retrograde doping profile where the doping concentration increases with depth below the word line, rather than decreasing. This inversion of the conventional doping gradient creates a higher doping concentration in the channel region beneath the word line, which suppresses leakage current and prevents row hammer-induced data loss while maintaining manufacturing feasibility through ion implantation processes
2Reliability
If the doping concentration in the channel is increased to suppress leakage, then row hammer resistance improves, but threshold voltage may be adversely affected
Solution Approach 1:
The patent applies local quality by creating a spatially varying doping concentration profile where the doping level is locally increased specifically in the channel region beneath the word line through retrograde ion implantation. This localized doping enhancement suppresses leakage current in the critical row hammer vulnerability zone while maintaining appropriate threshold voltage characteristics in other regions, thus achieving leakage suppression without adverse threshold voltage effects
3Productivity
If a buried word line structure is implemented to improve integration, then device integration increases, but vulnerability to row hammer phenomenon increases
Solution Approach 1:
The patent resolves this contradiction by changing the doping parameter profile in the buried word line structure. By implementing a retrograde doping profile with peak concentration beneath the word line rather than at the surface, the structure maintains its high integration benefits while the enhanced subsurface doping concentration suppresses leakage current that would otherwise cause row hammer-induced data loss, thus preserving both integration and data integrity
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 solution effectively suppresses data loss and enhances the semiconductor device's electrical properties and reliability by increasing the doping concentration of the channel, thus improving row hammer characteristics without undesirable variations in cell characteristics.
Implementation Method 1
A channel in the substrate underlies the word line and has an ion implantation region providing a retrograde doping profile that increases in concentration away from the word line
Data Source
AI summary
A device isolation region is formed, delimiting an active region in a substrate. A word line is formed, extending across the active region and the device isolation region and buried therein. A bit line is formed crossing the word line on the substrate. A channel is formed adjacent the word line, the channel having a retrograde doping profile having a doping concentration that increases away from a top surface of the active region. Formation of the channel includes performing a field ion implantation in the active region having a projected range near a bottom of the device isolation region.