MIS Contact Structures Using Segmented Silicide Layers
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Solution Overview
Problem
The formation of metal silicide regions in advanced transistor devices, such as those using silicon germanium or III-V materials, faces challenges like increased contact resistance, interfacial oxide formation, undesired diffusion of silicide materials, and agglomeration, which affect device performance and yield, especially in reduced-size contact openings.
Innovation Solution
The method involves forming MIS contact structures through a series of conformal deposition processes, including a contact ion implantation process, using materials like zirconium oxide or hafnium oxide, and a conductive cap layer, to create a lower resistance structure that overfills the contact opening and removes excess material, thereby reducing thermal budget constraints and improving contact quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal silicide regions are formed in reduced-size contact openings, then contact resistance is reduced, but agglomeration and non-continuous layer formation occur
Solution Approach 1:
The contact structure is divided into multiple discrete layers: a first conductive layer (metal silicide) and a second conductive layer (different material), each deposited separately. This segmentation prevents agglomeration by controlling the thickness and composition of each individual layer, while maintaining low contact resistance through the combined structure.
Solution Approach 2:
The contact structure uses composite materials consisting of two different conductive materials stacked together. The first conductive layer (e.g., cobalt silicide) provides initial contact, while the second conductive layer (e.g., tungsten or copper) provides additional conductivity and structural stability, preventing agglomeration in reduced-size contacts.
2Reliability
If additional heating processes are performed to convert metal silicide to lower resistance phase, then contact resistance is reduced, but thermal budget is reduced and device damage may occur
Solution Approach 1:
Instead of using additional heating processes to convert metal silicide to lower resistance phase, the invention changes the material parameters by selecting specific conductive materials with inherently low resistance in their stable phases. The second conductive layer is chosen to have lower resistance than the first layer, eliminating the need for aggressive thermal processing.
Solution Approach 2:
The first conductive layer (metal silicide) serves as a temporary, sacrificial layer that provides initial contact functionality but is eventually replaced or supplemented by the second conductive layer with superior electrical properties. This disposable approach avoids the need for additional heating to convert the first layer.
3Productivity
If device dimensions are decreased to increase packing density, then chip area utilization is improved, but contact opening size must be reduced leading to formation difficulties
Solution Approach 1:
The contact structure is segmented into multiple thin layers rather than forming a single thick contact in reduced-size openings. This segmentation makes the formation process easier to control in small dimensions, as each thin layer can be deposited conformally without requiring complex self-organization or agglomeration processes.
Solution Approach 2:
The invention replaces mechanical/self-organizing processes (agglomeration) with controlled deposition processes. Instead of relying on material self-assembly in reduced-size contacts, the contact structure is built layer-by-layer using standard deposition techniques, making formation easier and more reliable at smaller dimensions.
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 enhances the efficiency and effectiveness of MIS contact structures, reducing contact resistance and preventing agglomeration, leading to improved device performance and yield, particularly in high packing density applications.
Implementation Method 1
performing a contact ion implantation process to form a contact ion implant region comprising a contact ion that is positioned at least partially in at least one of the first, second or third layers of material
Data Source
AI summary
One method disclosed herein includes performing a plurality of conformal deposition processes to form first, second and third layers of material within a contact opening, wherein the first layer comprises a contact insulating material, the second layer comprises a metal-containing material and the third layer comprises a conductive cap material, wherein the third layer is positioned above the second layer. The method further includes forming a contact ion implant region that is positioned at least partially in at least one of the first, second or third layers of material, forming a conductive material above the third layer and removing portions of the layers of material positioned outside of the contact opening.