Gate Electrode Grain Size Control for Low Resistance and Adhesion
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Solution Overview
Problem
Existing methods for fabricating gate and contact structures in conductive circuits often result in poor quality due to high electrical resistance and poor adhesion of large conductive material grains, leading to over-polishing and potential dysfunction.
Innovation Solution
A method involving the deposition of two layers of conductive material with different grain sizes, where a first layer with larger grains is partially removed, and a second layer with smaller grains is deposited, followed by planarization, to achieve a conductive structure with low resistance and high adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single layer of conductive material is deposited to fill openings, then the opening can be completely filled, but the resulting structure exhibits high electrical resistance and poor adhesion due to large grain sizes
Solution Approach 1:
The conductive material deposition is divided into two separate layers with different grain size characteristics. The first layer contains larger grains that provide good adhesion, while the second layer contains smaller grains that provide low electrical resistance. This segmentation allows each layer to optimize for its specific function rather than requiring a single layer to satisfy conflicting requirements.
Solution Approach 2:
Different regions of the conductive structure are given different grain size properties. The bottom layer (first conductive layer) has larger grains optimized for adhesion to the substrate, while the top layer (second conductive layer) has smaller grains optimized for low electrical resistance. This local differentiation of material properties resolves the contradiction between adhesion and resistance requirements.
2Manufacturing precision
If chemical-mechanical planarization is applied to remove excess conductive material, then planarization is achieved, but large grains are over-polished leading to dysfunction
Solution Approach 1:
The conductive structure is segmented into two layers with different grain sizes, where the top layer consists of smaller grains that are more resistant to over-polishing during chemical-mechanical planarization. This segmentation protects the underlying larger grains from being exposed through excessive removal, maintaining the structural integrity and functionality of the conductive element.
Solution Approach 2:
The second layer of conductive material with smaller grains acts as a protective cushion over the first layer with larger grains. During chemical-mechanical planarization, this top layer absorbs the excessive removal action, preventing the larger grains in the first layer from being over-polished and exposed, thereby cushioning against potential dysfunction.
3Reliability
If conventional single-layer deposition is used, then the process is simple, but the electrical resistance is high and adhesion is poor
Solution Approach 1:
The deposition process is segmented into two distinct deposition steps creating two separate conductive layers. This segmentation enables optimization of each layer's grain structure for specific performance requirements, achieving superior conductive performance despite the increased process complexity.
Solution Approach 2:
The conductive structure employs a composite approach with two different conductive material layers, each with distinct grain size characteristics. This composite structure combines the advantages of large grains (adhesion) and small grains (low resistance) into a single functional element, improving overall conductive performance.
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 allows for complete filling of openings and high planarization of gate or contact structures while maintaining low resistance, overcoming the deficiencies of previous methods.
Implementation Method 1
depositing a first conductive material within the opening, at least a first portion of the deposited first conductive material comprising grains of a size larger than a defined value
Implementation Method 2
depositing a second conductive material within the opening over the first conductive material, at least a second portion of the deposited second conductive material comprising grains of a size less than the defined value
Implementation Method 3
the removing of the first conductive material can performed by a reactive ion etching process or a wet etching process
Implementation Method 4
the method can further comprise removing a part of the second conductive material by a chemical-mechanical planarization (CMP) process
Data Source
AI summary
A conductive structure(s), such as a gate electrode(s) or a contact structure(s), and methods of fabrication thereof are provided. The conductive structure(s) includes a first conductive layer of a first conductive material, and a second conductive layer of a second conductive material. The second conductive layer is disposed over the first conductive layer, and at least a portion of the first conductive material includes grains having a size larger than a defined value, and at least a second portion of the second conductive material includes grains having a size less than the defined value. In one embodiment, the first and second conductive materials are the same conductive material, with different-sized grains.