Epitaxial Layer Strain Control in Semiconductor Structures
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Solution Overview
Problem
The complexity of processing and manufacturing integrated circuits (ICs) has increased due to the need for varying levels of strain in semiconductor structures, specifically higher strain in dense regions and lower strain in isolated regions, which existing technologies struggle to effectively manage.
Innovation Solution
A method for fabricating semiconductor structures with epitaxial layers involves dividing a substrate into dense and isolated regions, forming specific gate structures, and using multiple material layers to create recesses that are filled with an epitaxial layer, allowing for controlled strain distribution by etching and masking processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If higher strain is applied to dense regions and lower strain to isolated regions, then carrier mobility is enhanced, but processing complexity increases
Solution Approach 1:
The substrate is divided into dense regions and isolated regions, with different material layer configurations applied to each region. The second material layer is selectively removed only in dense regions, creating distinct structural segments that enable different strain levels in different regions without requiring complete redesign of the entire structure.
Solution Approach 2:
Different strain levels are applied locally to different regions of the substrate. The dense regions receive higher strain through the presence of the second material layer, while isolated regions receive lower strain with the second material layer removed. This local differentiation optimizes carrier mobility in each region according to its specific requirements without uniformly increasing processing complexity across the entire device.
2Manufacturing precision
If multiple material layers are formed and selectively removed, then different channel strains are achieved, but manufacturing steps increase
Solution Approach 1:
The first material layer is formed to cover both dense and isolated regions before the second material layer is deposited. This preliminary configuration allows subsequent selective removal of the second material layer in dense regions while preserving it in isolated regions, achieving precise strain control through a systematic sequence of operations that can be integrated into existing manufacturing workflows.
Solution Approach 2:
The first material layer serves as an intermediary structure that is present in both dense and isolated regions. By forming this layer first and then selectively removing the second material layer in dense regions, the process achieves precise strain differentiation. The first material layer acts as a foundation that enables the selective strain application without requiring complete restructuring of the entire device.
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 method enables the achievement of different channel strains within dense and isolated regions, enhancing carrier mobility and simplifying the manufacturing process by precisely controlling strain levels, thereby improving IC performance.
Implementation Method 1
Strained silicon is formed by epitaxially growing silicon on materials that have a different lattice constant from silicon
Implementation Method 2
as an epitaxial layer such as SiGe has a different lattice constant from Si, there will be a lattice mismatch between a SiGe substrate and epitaxial Si grown thereon, and such a lattice mismatch will induce strain in an epitaxial Si layer
Data Source
AI summary
A fabricating method of a semiconductor structure includes providing a substrate divided into a dense region and an isolated region, wherein a first gate structure is disposed within the dense region, and a second gate structure is disposed within the isolated region. Then, a first material layer is formed to cover the first gate structure, the second gate structure and the substrate. Later, a second material layer is formed to cover the first material layer. After that, the second material layer within the dense region is entirely removed. Subsequently, a third material layer is formed to cover the isolated region and the dense region. Next, the substrate is etched to forma first recess at two sides of the first gate structure, and a second recess at two sides of the second gate structure. Finally, an epitaxial layer is formed to fill the first recess and the second recess.