Strained Stacked Nanosheet FET Stress Liner Strain Retention
Solution Overview
Problem
The loss of strain at the ends of semiconductor fins during the cutting process in CMOS devices leads to device degradation and variation, as the induced strain relaxes, affecting the performance of field effect transistors.
Innovation Solution
The method involves forming stress liners at the ends of semiconductor fins, using compressive or tensile stress depending on the type of transistor, and etching away the sacrificial material to suspend the channel material layers between the stress liners, maintaining strain and enhancing device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a strained semiconductor fin is cut to length, then the device can be manufactured with specific dimensions, but the induced strain relaxes at the fin ends causing device degradation
Solution Approach 1:
Stress liners are formed at the fin ends before the fin is cut to length. These pre-formed stress liners maintain the strain at the fin ends even after cutting, preventing strain relaxation and the associated device degradation. The preliminary formation of stress liners ensures that when the fin is subsequently cut to the required length, the strain is already in place and preserved.
Solution Approach 2:
The patent changes the physical state and properties of the fin ends by forming stress liners with specific stress characteristics (tensile or compressive) that counteract the strain relaxation. By modifying the stress state at the fin ends through the stress liners, the device maintains the necessary strain for optimal performance despite the dimensional change from cutting.
2Reliability
If stress liners are formed at the ends of fins, then strain is maintained at the fin ends, but the manufacturing process becomes more complex
Solution Approach 1:
The formation of stress liners is merged with existing manufacturing steps such as the dielectric fill process or epitaxial growth process. By combining the stress liner formation with these already-planned process steps, the patent avoids adding significant complexity to the manufacturing process while still achieving the goal of maintaining strain at the fin ends.
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 at the ends of semiconductor fins, improving the conductivity and reliability of field effect transistors by preventing strain relaxation, thus enhancing device performance and reducing variation.
Implementation Method 1
Stress liners are formed in contact with both ends of the fin of alternating channel material and sacrificial material layers. The stress liners exert a stress on the fin.
Data Source
AI summary
Methods of forming a semiconductor device include forming stress liners in contact with both ends of a fin of alternating channel material and sacrificial material layers. The stress liners exert a stress on the fin. The sacrificial material is etched away from the fin, such that the layers of the channel material are suspended between the stress liners. A gate stack on the suspended layers of channel material.