SRAM Transistor Impurity Profile for Noise and Stability
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Solution Overview
Problem
Existing semiconductor memory technologies face challenges in achieving stable operation and high integration density due to variations in transistor current ratios and noise levels, particularly in SRAM-type units, where minimizing transistor size affects current ratios and noise performance.
Innovation Solution
The implementation of a SRAM-type unit cell with a first transistor of one conductivity type and a second transistor of a different conductivity type, where the impurity concentration is strategically varied across the channel width to optimize effective channel width and reduce noise, using a manufacturing method that involves precise ion implantation and element isolation techniques to form transistors with overlapping gate electrodes and semiconductor regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the transistor size is minimized to achieve high integration density, then the integration density is improved, but the current ratio becomes unstable and noise increases
Solution Approach 1:
The invention applies local quality by creating a non-uniform impurity concentration distribution within the active region. Specifically, the impurity concentration is set to be higher at positions adjacent to the gate electrode than at the center position, forming a localized high-concentration region that stabilizes the current ratio without increasing overall transistor size, thus resolving the contradiction between integration density and current ratio stability.
2Productivity
If the transistor size is minimized to achieve high integration density, then the integration density is improved, but the noise level increases
Solution Approach 1:
The invention reduces noise by creating a localized high impurity concentration region adjacent to the gate electrode. This local quality modification suppresses short-channel effects and hot carrier effects that generate noise, allowing miniaturized transistors to operate with lower noise levels while maintaining high integration density.
3Reliability
If the impurity concentration is increased to stabilize current ratio, then the current ratio stability is improved, but the noise increases due to higher impurity scattering
Solution Approach 1:
The invention resolves this contradiction by applying local quality - increasing impurity concentration only in specific regions adjacent to the gate electrode rather than uniformly throughout the active region. This localized approach stabilizes the current ratio through enhanced carrier control near the channel while minimizing bulk impurity scattering that would increase noise.
Solution Approach 2:
The invention segments the active region into zones with different impurity concentrations: a high-concentration region adjacent to the gate electrode and a lower-concentration region at the center. This segmentation allows the high-concentration zone to stabilize current ratio while the low-concentration zone maintains low noise performance.
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 stabilizes the operation of SRAM-type memory units by maintaining a desirable current ratio and reducing noise, enabling higher integration density and improved performance by controlling channel width and impurity concentration profiles.
Implementation Method 1
performing implantation of impurity ions of the first conductivity on the semiconductor substrate via the second groove
Data Source
AI summary
A semiconductor device has a first transistor of a first conductivity type and a second transistor of a second conductivity type, the first transistor is arranged in an active region of a semiconductor substrate, and a gate electrode and the active region overlap with each other in a plan view and also have a portion located between the source and the drain of the first transistor of the semiconductor substrate. In the channel width direction, an impurity concentration of the second conductivity type is higher at the end than on the center side of the portion.