Strained SOI Substrate Lateral Recrystallization
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Solution Overview
Problem
Existing methods for producing strained semiconductor on insulator substrates face challenges in efficiently relaxing mechanical strains in transistors, particularly for P-type transistors, due to amorphization and recrystallization processes that can introduce dislocations and require restrictive thermal budgets.
Innovation Solution
A method involving amorphization of specific regions on the semiconductor surface while maintaining the crystalline structure of adjacent areas, followed by lateral recrystallization using the crystalline areas as starting points for recrystallization fronts, allowing for relaxation of mechanical strains without vertical recrystallization and enabling the production of substrates with both tensile and compressive strained regions for improved transistor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If localized implantation amorphization is performed to relax strain in PMOS transistor regions, then mechanical strain relaxation is achieved, but dislocations are introduced in the transistors
Solution Approach 1:
The patent applies preliminary action by performing amorphization and recrystallization on the semiconductor layer before transistor fabrication. This allows strain relaxation to occur in the future PMOS regions prior to device formation, avoiding the need for post-transistor amorphization that would introduce dislocations. The crystalline structure is restored before any transistor processing begins, ensuring high device quality.
Solution Approach 2:
The patent segments the semiconductor layer into distinct regions with different strain states before transistor fabrication. By selectively amorphizing and recrystallizing specific areas, the layer is divided into tensile-strained regions (for NMOS) and relaxed/compressive regions (for PMOS), allowing each transistor type to have optimized strain characteristics without compromising the other.
2Stability of the object's composition
If recrystallization is performed after transistor production, then strain relaxation is achieved, but thermal budget management becomes restrictive
Solution Approach 1:
The patent performs the energy-intensive amorphization and recrystallization process before transistor fabrication rather than after. This preliminary action allows the use of optimized thermal cycles for strain relaxation without the constraints of subsequent transistor processing requirements. The thermal budget is managed more efficiently by completing the recrystallization early when the structure is more tolerant of thermal processing.
3Stability of the object's composition
If gate stack is present during strain relaxation, then transistor structure is maintained, but efficient relaxation of channel region mechanical strains becomes difficult
Solution Approach 1:
The patent removes or avoids forming the gate stack before performing the amorphization and recrystallization process. This preliminary action allows the channel region to be fully accessed and uniformly recrystallized without the gate structure obstructing the process. After strain relaxation is complete, the gate stack is then formed, ensuring both efficient strain relaxation and proper transistor structure.
4Reliability
If tensile strained silicon layer is produced for NMOS transistors, then NMOS performance is improved, but P-type transistor production becomes detrimental
Solution Approach 1:
The patent applies local quality by creating spatially varying strain characteristics in the semiconductor layer. Different regions are selectively amorphized and recrystallized to produce tensile strain in NMOS regions and relaxed or compressive strain in PMOS regions. This allows each transistor type to have locally optimized strain conditions while sharing the same substrate and processing flow.
Solution Approach 2:
The patent segments the semiconductor layer into functionally distinct regions with different strain states. By performing selective amorphization and recrystallization, the layer is divided into zones suitable for different transistor types, enabling both NMOS and PMOS fabrication on the same substrate with optimized performance for each device type.
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 relaxes mechanical strains in semiconductor substrates, enabling the production of transistors with improved performance by avoiding dislocation introduction and reducing thermal budget requirements, allowing for the formation of both N-type and P-type transistors with optimized channel regions.
Implementation Method 1
carrying out a recrystallization of the region by using at least one lateral face of the area of crystalline strained semi-conductor material in contact with the region as a starting area of a recrystallization front
Implementation Method 2
amorphizing at least one region of the semi-conductor material of the superficial layer while keeping the crystalline structure of at least one area of the superficial layer of strained semi-conductor material adjoining the region
Data Source
AI summary
A method is provided for producing a microelectronic device provided with different strained areas in a superficial layer of a semi-conductor on insulator type substrate, including amorphizing a region of the superficial layer and then a lateral recrystallization of the region from crystalline areas adjoining the region.