DRAM Contact Leakage Reduction via Local Doping
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Solution Overview
Problem
Integrated circuits, particularly DRAMs, face performance degradation due to leakage current in contact regions, which leads to charge loss and reduced data retention time, complicating the manufacturing process and requiring complex structures.
Innovation Solution
A method for manufacturing a low-leakage contact in MOS transistor devices involves forming a substrate with well structures, implanting impurities for threshold voltage adjustment, creating a gate stack, and forming lightly doped drain structures, spacers, and contact structures while using photo resist masks to prevent threshold voltage implantation in certain regions, thereby reducing leakage current and contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If threshold voltage implantation is performed to adjust transistor characteristics, then transistor performance is improved, but leakage current increases in contact regions
Solution Approach 1:
The patent applies different doping concentrations to different regions: the channel region receives threshold voltage implantation with higher dopant concentration to improve transistor performance, while the contact region maintains lower dopant concentration to minimize leakage current. This spatial differentiation of doping quality resolves the contradiction between performance enhancement and leakage reduction.
Solution Approach 2:
The patent segments the doping process into distinct stages and regions. First, threshold voltage implantation is performed on the channel region, then contact region doping is performed separately with controlled concentration. This segmentation allows independent optimization of each region's electrical characteristics, achieving both improved transistor performance and reduced contact leakage.
2Object-generated harmful factors
If complex manufacturing processes are used to reduce leakage, then leakage current is reduced, but device complexity increases
Solution Approach 1:
The patent employs self-aligned doping processes where previously formed structures (such as gate electrodes or isolation regions) automatically serve as masks for subsequent doping steps. This eliminates the need for additional complex masking processes, reducing manufacturing complexity while achieving precise spatial control over doping concentrations to minimize leakage current.
Solution Approach 2:
The patent controls leakage current by adjusting doping concentration parameters rather than adding complex structural elements. By optimizing the dopant concentration in the contact region to be lower than in the channel region, the patent achieves leakage reduction through parameter optimization alone, avoiding increased device or process complexity.
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 method results in improved device yields, reduced leakage current, lower contact resistance, and extended data retention time, allowing for longer intervals between refresh operations in DRAM memory devices.
Implementation Method 1
implanting impurities for threshold voltage adjustment into the first region using the patterned photo resist as a mask
Implementation Method 2
a gate dielectric layer is grown to overlie the surface region
Data Source
AI summary
A semiconductor integrated circuit device includes a substrate, a well structure within the substrate, a first region, a second region, and multiple isolation regions within the well structure. The device further includes a channel region within the first region, a gate dielectric layer overlying the channel region, and a gate stack overlying the gate dielectric layer, the gate stack includes a silicide layer overlying a polysilicon layer. The device additionally includes LDD structures on sides of the channel region and spacers on sides of the gate stack. Furthermore, the device includes a source region and a drain region and a contact structure over the source region, and a junction between the contact structure and the source region being within the second region.