Ruthenium S/D Contact Structure to Prevent Voids and Resistance
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Solution Overview
Problem
The semiconductor industry faces challenges in scaling down contact structures to achieve higher transistor densities due to increased contact resistance and void formation caused by cobalt diffusion, which reduces IC performance and yield.
Innovation Solution
A contact structure made of platinum-group metallic materials, such as ruthenium, is used, eliminating the need for a barrier liner to prevent void formation and reduce resistance, while ensuring adhesion to dielectric layers, thus enhancing structural integrity and effective contact area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cobalt is used as the conductive material in contact structures, then lower resistivity is achieved, but void formation occurs due to cobalt diffusion
Solution Approach 1:
The patent removes cobalt from the contact structure composition entirely, extracting the harmful element that causes void formation through diffusion. This is achieved by replacing cobalt with copper or aluminum, which do not exhibit the same diffusion behavior into the surrounding dielectric materials, thereby eliminating the root cause of void formation while maintaining electrical conductivity.
Solution Approach 2:
The patent introduces a liner layer as an intermediary barrier between the conductive material and the surrounding dielectric. This liner acts as a diffusion barrier that prevents metal atoms from migrating into adjacent structures. The liner is selectively removed only in the contact hole region to establish electrical contact, while remaining intact in vias to prevent diffusion, thus mediating between the conductive material and the dielectric environment.
2Reliability
If a barrier liner is added to prevent cobalt diffusion, then void formation is reduced, but contact resistance increases
Solution Approach 1:
The patent extracts the barrier liner from the contact structure where it would increase resistance, by selectively removing it only in the contact hole region. Simultaneously, the liner is retained in via regions where it serves as a diffusion barrier. This selective extraction approach eliminates the harmful effect of increased contact resistance while preserving the beneficial diffusion prevention function in appropriate locations.
Solution Approach 2:
The patent applies different structural configurations to different regions: contact holes have no liner to minimize resistance, while vias retain the liner to prevent diffusion. This local differentiation of structure quality allows optimization for each specific function - electrical contact in one region and diffusion barrier in another - resolving the contradiction between low resistance and void prevention.
3Productivity
If contact structure dimensions are scaled down to increase transistor density, then higher device capacity is achieved, but contact resistance increases
Solution Approach 1:
The patent changes the material parameter from cobalt to copper or aluminum, which have different electrical and diffusion properties. This material substitution allows for smaller contact dimensions without proportionally increasing resistance, as copper and aluminum maintain lower resistivity at scaled dimensions compared to cobalt-based structures, thereby enabling higher transistor density without the penalty of excessive contact resistance.
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 platinum-group metallic material contact structure reduces resistance and prevents void formation, leading to improved IC yield and reliability by maintaining structural integrity and increasing effective contact area without the need for a barrier liner.
Implementation Method 1
The contact structure can include a liner structure disposed between the metallic material and the dielectric layer. The liner structure can include titanium, tungsten, tantalum, or a nitride or oxide thereof.
Implementation Method 2
the metallic material can have a sufficient adhesion to the contact structure's adjacent dielectric layers
Data Source
AI summary
The present disclosure describes a semiconductor structure and a method for forming the same. The semiconductor structure can include a substrate, a gate structure over the substrate, a layer of dielectric material over the gate structure, a source/drain (S/D) contact layer formed through and adjacent to the gate structure, and a trench conductor layer over and in contact with the S/D contact layer. The S/D contact layer can include a layer of platinum-group metallic material and a silicide layer formed between the substrate and the layer of platinum-group metallic material. A top width of a top portion of the layer of platinum-group metallic material can be greater than or substantially equal to a bottom width of a bottom portion of the layer of platinum-group metallic material.