Stepped Semiconductor Structure With Boron Barrier Against DRAM Leakage
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Solution Overview
Problem
Recessed access devices in DRAMs experience leakage issues that can reduce performance and lead to failure during margin tests due to uncontrolled current flow between activated and non-activated portions.
Innovation Solution
A semiconductor structure is created with a substrate having a boron-implanted p-type surface, where a stepped structure is formed through etching and dielectric layers are deposited to block leakage, ensuring the p-type surface prevents current diffusion and enhances performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If recessed access device is activated, then access function is improved, but leakage current is generated that reduces performance
Solution Approach 1:
The patent applies local quality by creating a p-type surface region specifically at the recessed access device location through boron implantation. This localized doping creates a high-concentration p-type region that acts as a barrier to leakage current, while leaving other regions of the substrate unchanged. The selective modification of only the necessary area resolves the contradiction by providing leakage blocking exactly where needed without affecting overall device performance.
Solution Approach 2:
The patent introduces an intermediary p-type surface layer between the activated recessed access device and the surrounding n-type regions. This intermediate p-type region, created by boron implantation, serves as a barrier that prevents direct leakage current flow. The intermediary layer mediates the interaction between activated and non-activated portions, blocking harmful leakage while maintaining necessary electrical connections.
2Reliability
If recessed access device is activated, then access function is improved, but leakage current causes failure during margin test
Solution Approach 1:
The boron implantation creates a localized high-concentration p-type region at the recessed access device surface. This local modification provides a targeted barrier against leakage current diffusion, preventing the harmful effects from spreading to adjacent non-activated portions. The localized nature of the treatment ensures improved margin test performance without introducing widespread changes that could cause new problems.
3Reliability
If boron implantation is performed on first top surface, then leakage is blocked, but manufacturing process complexity increases
Solution Approach 1:
The boron implantation is performed as a preliminary action during the substrate preparation stage, before the recessed access devices are fully formed and before subsequent processing steps. By introducing the leakage-blocking p-type region early in the manufacturing sequence, the process integrates smoothly with existing fabrication flows without requiring additional complex steps later in production.
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 boron-implanted surface effectively blocks leakage, improving semiconductor structure performance and preventing failure during margin tests by isolating active areas, thus enhancing the overall reliability and efficiency of the semiconductor structure.
Implementation Method 1
The first top surface of the substrate is implanted by boron to increase a p-type concentration of the first top surface of the substrate
Implementation Method 2
the leakage may be blocked by the first top surface of the substrate such that the leakage is unable to diffuse to other portions of the substrate
Data Source
AI summary
A manufacturing method of a semiconductor structure includes: etching a substrate such that the substrate has a first top surface and a second top surface higher than the first top surface; implanting the first top surface of the substrate by boron to increase a p-type concentration of the first top surface of the substrate; forming a first dielectric layer on the substrate; and forming a second dielectric layer on the first dielectric layer.