FinFET Germanium Concentration Gradient Strain
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Solution Overview
Problem
Fin Field Effect Transistors (FinFETs) face challenges in achieving uniform stress distribution and hole mobility due to the relaxation of strain in the fin structure, which affects the performance of the transistor.
Innovation Solution
A semiconductor apparatus and method that utilize a substrate with a stack comprising a first material and a second material, such as silicon and germanium, with multiple concentrations of germanium to induce strain and compensate for relaxation, forming a fin with a source and drain, where the germanium concentrations are arranged in gradients or periodic elements to maintain constant stress and enhance hole mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a uniform concentration of second material is used in the stack, then the manufacturing process is simple, but the stress distribution becomes non-uniform due to strain relaxation
Solution Approach 1:
The patent applies local quality by varying the concentration of the second material (e.g., germanium) at different positions within the stack. Specifically, the concentration increases from the bottom layer adjacent to the substrate to the top layer, creating a graded structure. This spatial variation in material composition enables uniform stress distribution throughout the fin channel, compensating for strain relaxation effects that would otherwise occur in uniformly composed structures.
Solution Approach 2:
The patent implements parameter changes by systematically varying the concentration parameter of the second material across different layers of the stack. The concentration gradient is designed such that lower layers have lower concentrations while upper layers have higher concentrations. This parameter variation allows the structure to maintain constant stress levels despite the relaxation phenomenon, thereby improving device performance without complicating the manufacturing process.
2Ease of manufacture
If strain relaxation occurs in the fin structure, then the manufacturing process is straightforward, but hole mobility deteriorates
Solution Approach 1:
The patent addresses hole mobility degradation by implementing local quality through a graded concentration profile of the second material. Each layer in the stack has a specific concentration tailored to its position, with concentrations increasing from bottom to top. This localized compositional control creates uniform stress distribution that maintains high hole mobility throughout the channel, preventing the mobility deterioration that would result from uniform strain relaxation.
Solution Approach 2:
The patent resolves the hole mobility issue through parameter changes in the material composition. By varying the concentration parameter of the second material across the stack height, the invention creates a stress profile that compensates for relaxation effects. This parameter optimization ensures that hole mobility remains high and uniform throughout the channel, thereby improving device reliability while maintaining manufacturing feasibility.
3Stress or pressure
If the concentration of second material is increased to maintain stress, then stress distribution improves, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the stack into multiple discrete layers, each with a specific concentration of the second material. This layered structure allows precise control over the stress profile by adjusting the concentration in each segment. The segmentation approach enables uniform stress distribution while keeping the overall device structure manageable and manufacturable, as each layer can be deposited using standard semiconductor fabrication techniques.
Solution Approach 2:
The patent utilizes composite materials by combining the first material (e.g., silicon) with the second material (e.g., germanium) in varying concentrations across different layers. This composite structure, with its graded composition, achieves uniform stress distribution without requiring complex device architectures. The composite approach leverages the beneficial properties of both materials while managing structural complexity through controlled compositional variation.
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
The solution achieves a substantially constant stress distribution and improved hole mobility along the channel of the fin, enhancing the performance of the FinFET by maintaining uniform stress from the substrate to the top of the fin, thereby optimizing transistor performance.
Implementation Method 1
a strain induced in the stack via the substrate
Implementation Method 2
the stack comprises: a strain induced in the stack via the substrate; the first material and a second material
Implementation Method 3
the fin formed from the stack by etching away one or more portions of the stack
Data Source
AI summary
An apparatus of a semiconductor is provided wherein the apparatus comprises a substrate, a stack, and a fin. The substrate supports the stack and the substrate comprises a first material. The stack provides for the fin and the stack comprises: a strain induced in the stack via the substrate; the first material and a second material; and a plurality of concentrations of the second material with respect to the first material. The fin provides a source and a drain of a field effect transistor.