Metal Contact Plug Corrosion Reduction via CMP Slurry Ion Addition
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Solution Overview
Problem
Metal contact plugs in MOS devices are prone to corrosion during Chemical Mechanical Polishing (CMP) and fine polishing steps, especially in isolated plug regions, as feature sizes shrink, leading to recesses and corrosion issues exacerbated by the use of reactive metals.
Innovation Solution
Incorporating a metal ion source compound corresponding to the metal used in the contact plugs into the CMP slurry and polishing rinse, such as cobalt or tungsten ions, to reduce corrosion and recess formation by shifting the chemical equilibrium and slowing down corrosion reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If CMP and fine polishing steps are performed on metal contact plugs, then planarization and surface finish are improved, but corrosion and recess formation occur
Solution Approach 1:
A corrosion inhibitor is introduced as an intermediary substance in the CMP slurry and polishing rinse to mediate between the mechanical polishing action and the metal contact plug. The inhibitor forms a protective layer on the metal surface during polishing, preventing direct contact between corrosive elements in the slurry/rinse and the metal, thus allowing planarization to proceed while protecting against corrosion
Solution Approach 2:
The chemical composition parameters of the CMP slurry and polishing rinse are modified by adding corrosion inhibitor compounds. This changes the chemical environment from corrosive to protective, allowing the mechanical polishing function to be maintained while the chemical corrosion effect is suppressed. The inhibitor concentration and chemical properties are optimized to achieve both good polishing results and corrosion protection
2Length of moving object
If feature sizes are reduced to improve device scaling, then device density and integration are improved, but corrosion and recess issues are exacerbated
Solution Approach 1:
The corrosion protection is applied locally at the contact plug surface where it is most needed during polishing. The corrosion inhibitor accumulates preferentially on the metal contact plug surface, providing localized protection where the metal is exposed to the CMP slurry and rinse. This local quality approach ensures that small feature sizes are protected without requiring universal changes to the entire processing system
Solution Approach 2:
The corrosion inhibitor acts as a local intermediary layer on the contact plug surface, particularly important for small features where surface-to-volume ratio is high. This protective layer prevents direct exposure of the entire contact plug surface to corrosive elements during polishing, maintaining dimensional integrity even when feature sizes are reduced for scaling
3Reliability
If reactive metals are used to improve electrical conductivity, then device performance is improved, but susceptibility to corrosion during polishing increases
Solution Approach 1:
The reactive nature of the metal, which causes high corrosion susceptibility, is converted into a benefit through the use of corrosion inhibitor. The inhibitor specifically targets and protects the reactive metal surface, transforming the harmful reactivity into a controlled interaction where the metal's chemical activity is harnessed to form protective metal inhibitor complexes that actually protect the underlying metal from further corrosion
Solution Approach 2:
A corrosion inhibitor intermediary is introduced to mediate between the reactive metal and the corrosive environment in the CMP slurry and rinse. The inhibitor forms a protective complex with the reactive metal surface, preventing direct contact between the metal and corrosive elements. This allows reactive metals to be used for their superior electrical conductivity while the intermediary layer protects against the inherent corrosion susceptibility
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
Substantially diminishes corrosion and recess formation in metal contact plugs, maintaining high removal rates and avoiding detrimental side effects, with corrosion minimized to less than 2 nm depth and removal rates exceeding 30 nm/minute, even at 16 nm feature sizes.
Implementation Method 1
Incorporating a metal ion source compound corresponding to the metal used in the contact plugs into the CMP slurry and polishing rinse, such as cobalt or tungsten ions, to reduce corrosion and recess formation by shifting the chemical equilibrium and slowing down corrosion reactions
Data Source
AI summary
A method of manufacturing a device includes exposing at least one of a source/drain contact plug or a gate contact plug to a metal ion source solution during a manufacturing process, wherein a constituent metal of a metal ion in the metal ion source solution and the at least one source/drain contact plug or gate contact plug is the same. If the source/drain contact plug or the gate contact plug is formed of cobalt, the metal ion source solution includes a cobalt ion source solution. If the source/drain contact plug or the gate contact plug is formed of tungsten, the metal ion source solution includes a tungsten ion source solution.