NFET Gate Stack With Aluminum-Free Work-Function Layer
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Solution Overview
Problem
As semiconductor devices continue to shrink in size, the integration of electronic components poses challenges, particularly due to the degradation of gate stacks caused by aluminum, which affects the reliability of the resulting semiconductor devices.
Innovation Solution
The formation of an aluminum-free work-function layer in the gate stack, comprising a metal-containing layer and a silicon layer, reduces the work-function and enhances the reliability of the gate stack by eliminating aluminum, which is achieved through in-situ deposition processes to prevent oxidation and ensure nitridation of the silicon layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aluminum is used in the work-function layer, then the work-function is reduced and device performance is improved, but the reliability of the gate stack degrades
Solution Approach 1:
The patent removes aluminum from the work-function layer composition entirely, extracting the harmful element while maintaining the necessary electrical functionality through alternative material combinations (titanium nitride and silicon) that do not exhibit the same degradation mechanisms
Solution Approach 2:
The invention uses a composite structure consisting of titanium nitride and silicon layers to achieve the desired work-function characteristics without aluminum. This composite material approach allows optimization of both reliability and electrical performance by combining materials with complementary properties
2Reliability
If in-situ deposition is used, then oxidation is prevented and nitridation is ensured, but process complexity increases
Solution Approach 1:
The patent combines multiple deposition steps (metal layer deposition and silicon layer deposition) into a single in-situ process sequence, eliminating vacuum breaks and environmental exposures that would cause oxidation. This merging of steps prevents contamination while achieving the desired nitridation effect
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 aluminum-free gate stack improves the reliability and reduces gate resistance by up to 40% compared to conventional methods, ensuring consistent performance in advanced semiconductor devices.
Implementation Method 1
depositing a silicon-containing layer on the metal-containing layer... achieved through in-situ deposition processes
Implementation Method 2
ensure nitridation of the silicon layer
Data Source
AI summary
A method includes forming a dummy gate stack over a semiconductor region, forming a source/drain region on a side of the dummy gate stack, removing the dummy gate stack to form a trench, depositing a gate dielectric layer extending into the trench, depositing a metal-containing layer over the gate dielectric layer, and depositing a silicon-containing layer on the metal-containing layer. The metal-containing layer and the silicon-containing layer in combination act as a work-function layer. A planarization process is performed to remove excess portions of the silicon-containing layer, the metal-containing layer, and the gate dielectric layer, with remaining portions of the silicon-containing layer, the metal-containing layer, and the gate dielectric layer forming a gate stack.