Metal Gate Spacer Conversion to Prevent Contact Short Circuits
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Solution Overview
Problem
In the fabrication of metal gate transistors, the removal of polysilicon gate material leads to issues such as boron penetration, depletion effects, and short circuits due to the removal of spacer, contact etch stop layer, and interlayer dielectric, affecting device performance.
Innovation Solution
A method involving forming a metal gate with spacers and interlayer dielectric layers, followed by a plasma treatment to transform conductive materials into dielectric portions, and subsequent cleaning to prevent short circuits, ensuring proper layer formation and device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polysilicon gate material is removed during fabrication of metal gate transistor, then work function metal layer and low resistance metal layer can be deposited, but spacer, contact etch stop layer, and interlayer dielectric layer may be removed causing short circuit with adjacent contact plugs
Solution Approach 1:
The patent applies preliminary anti-action by performing a plasma treatment process before depositing work function metal and low resistance metal layers. This plasma treatment transforms the spacer, contact etch stop layer, and interlayer dielectric layer into dielectric portions with different etch selectivity, preventing them from being removed during subsequent processing steps that would otherwise cause short circuits with contact plugs.
Solution Approach 2:
The patent applies preliminary action by transforming the conductive materials into dielectric portions through plasma treatment before the deposition of metal layers. This preliminary transformation ensures that the spacer and related layers maintain their structural integrity and electrical insulation properties throughout the subsequent fabrication process, preventing premature short circuits.
2Ease of manufacture
If conventional polysilicon gate is used, then fabrication process is simple, but boron penetration and depletion effect occur reducing gate capacitance and driving force
Solution Approach 1:
The patent applies parameter changes by replacing the polysilicon gate material with a metal gate structure. This fundamental material parameter change eliminates boron penetration and depletion effects, significantly improving gate capacitance and driving force while maintaining fabrication process compatibility through the use of standard semiconductor manufacturing techniques.
Solution Approach 2:
The patent applies composite materials by using a multi-layer metal gate structure comprising work function metal layer and low resistance metal layer. This composite structure combines the advantages of different materials: the work function metal provides appropriate threshold voltage control while the low resistance metal reduces gate resistance, achieving superior gate performance compared to conventional polysilicon gates.
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 prevents short circuits and maintains device performance by transforming conductive materials into dielectric portions, ensuring accurate layer formation and preventing contact with adjacent contact plugs.
Implementation Method 1
performing a plasma treatment process to transform the spacer into a first bottom portion and a first top portion
Data Source
AI summary
A method for fabricating a semiconductor device includes the steps of forming a metal gate on a substrate, a spacer around the metal gate, and a first interlayer dielectric (ILD) layer around the spacer, performing a plasma treatment process to transform the spacer into a first bottom portion and a first top portion, performing a cleaning process to remove the first top portion, and forming a second ILD layer on the metal gate and the first ILD layer.