Strained Silicon Germanium Device Edge Strain Preservation
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Solution Overview
Problem
Strained silicon germanium-on-insulator (SGOI) technology experiences strain loss at the edges when patterned into separate active areas, leading to reduced strain benefit and device variability in fully depleted silicon-on-insulator (FDSOI) p-type field-effect-transistors (PFETs).
Innovation Solution
A method involving the formation of a strained silicon germanium layer on a substrate, with patterned hard mask layers and selective oxidation to create oxide regions that preserve strain without edge relaxation, defining active areas within the silicon germanium layer without physical etching, thereby maintaining compressive strain across the semiconductor structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the strained silicon germanium layer is patterned into separate active areas using conventional methods, then the active areas are defined, but strain loss occurs at the edges leading to reduced device performance
Solution Approach 1:
A sacrificial oxide layer is introduced as an intermediary between the strained silicon germanium layer and the pattern definition process. This oxide layer protects the edges of the semiconductor layer from strain relaxation during patterning, allowing active areas to be defined while maintaining strain uniformity across all regions including edges.
Solution Approach 2:
The sacrificial oxide layer is formed on the strained silicon germanium layer before the patterning process begins. This preliminary protective action prevents edge strain relaxation from occurring during subsequent etching and patterning steps, ensuring strain is maintained when active areas are defined.
2Strength
If the strained silicon germanium layer is kept continuous to maintain strain, then strain benefit is preserved, but device variability increases due to edge relaxation when patterned
Solution Approach 1:
The sacrificial oxide acts as a mediator that allows the strained silicon germanium layer to remain continuous and maintain strain benefit, while simultaneously protecting against edge relaxation during patterning. This enables both strain preservation and reduced device variability.
Solution Approach 2:
The physical and chemical properties of the semiconductor structure are changed by forming an oxide layer with different mechanical properties than the silicon germanium. This parameter change allows the structure to maintain strain while being patterned, as the oxide layer has different stress characteristics that prevent strain relaxation at edges.
3Ease of manufacture
If conventional patterning is used to define active areas, then manufacturing is simplified, but edge strain relaxation reduces the strain benefit
Solution Approach 1:
The sacrificial oxide layer serves as a temporary intermediary that enables conventional patterning processes to be used while protecting the strain benefit. The oxide is formed, conventional patterning is performed, and then the oxide is removed, achieving both ease of manufacture and strain preservation.
Solution Approach 2:
The sacrificial oxide layer is temporarily introduced to protect strain during patterning, then discarded after serving its protective function. This temporary addition enables conventional manufacturing processes while preserving the strain benefit, and the oxide is removed after patterning is complete.
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 effectively maintains strain across the semiconductor structure, reducing device variability and enhancing the performance of PFETs by preventing edge strain relaxation, thus improving the overall performance of SGOI in FDSOI technology.
Implementation Method 1
At least a first exposed portion and a second exposed portion of the strained silicon germanium layer are oxidized. The oxidizing process forms a first oxide region and a second oxide region within the first and second exposed portions, respectively, of the strained silicon germanium.
Data Source
AI summary
A method for forming a semiconductor structure includes forming a strained silicon germanium layer on top of a substrate. At least one patterned hard mask layer is formed on and in contact with at least a first portion of the strained silicon germanium layer. At least a first exposed portion and a second exposed portion of the strained silicon germanium layer are oxidized. The oxidizing process forms a first oxide region and a second oxide region within the first and second exposed portions, respectively, of the strained silicon germanium.