SiGe Channel Layer Mobility in DRAM Access Devices
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Solution Overview
Problem
The existing semiconductor devices, particularly DRAMs, face challenges in uniformly forming an ion-doped layer between the gate and substrate in recessed access devices, limiting carrier mobility and conductivity due to the difficulty in specifically and uniformly forming an ion-doped layer.
Innovation Solution
The semiconductor device employs a channel layer made of silicon-germanium or silicon-carbon epitaxial material, with varying germanium and carbon content from the substrate to the gate, and an epitaxial layer with similar materials, to enhance conductivity and mobility, and includes isolation structures and a gate stack formed using specific materials and processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an ion-doping process is used to increase conductivity and mobility, then carrier mobility and conductivity can be improved, but it is difficult to specifically and uniformly form an ion-doped layer between the gate and the substrate in recessed access devices
Solution Approach 1:
The patent changes the material parameter of the channel layer from pure silicon to silicon-germanium alloy with varying germanium content. The germanium content is specifically designed to increase from the substrate interface toward the gate, creating a gradient that improves carrier mobility and conductivity without requiring ion-doping processes. This material composition change resolves the contradiction by achieving high conductivity through inherent material properties rather than post-growth doping.
Solution Approach 2:
The patent employs composite materials by creating a silicon-germanium channel layer with non-uniform composition. The channel layer combines silicon and germanium in varying proportions throughout its thickness, with lower germanium content near the substrate and higher germanium content near the gate. This composite structure enables regions of high carrier mobility near the gate while maintaining structural integrity at the substrate interface, eliminating the need for ion-doping.
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 configuration improves the performance of the semiconductor device by increasing carrier mobility and conductivity, addressing the limitations of existing technologies in forming uniform ion-doped layers.
Implementation Method 1
A material of the channel layer is selected from the group consisting of silicon-germanium epitaxial material, silicon-carbon epitaxial material, and a combination thereof
Data Source
AI summary
The present disclosure provides a semiconductor device including a substrate, a gate structure, a channel layer, a first active region and a second active region. The gate structure is disposed in the substrate. The channel layer is sandwiched between the gate structure and the substrate. A material of the channel layer is selected from the group consisting of silicon-germanium epitaxial material, silicon-carbon epitaxial material, and a combination thereof. The first active region and the second active region are disposed in the substrate and respectively disposed at opposite sides of the gate structure. A method for manufacturing a semiconductor device is provided herein.