Selective Tungsten CVD Via Fill
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conformal fill approaches for filling vias with tungsten in semiconductor substrates result in limited tungsten grain growth and the formation of seams, leading to increased resistivity and compromised via resistance due to differences in nucleation delays between metal and dielectric surfaces.
Innovation Solution
A method utilizing selective chemical vapor deposition (CVD) tungsten growth from the bottom up, with a nucleation layer and growth interruption treatments, to fill vias while avoiding growth on dielectric surfaces and maximizing tungsten grain size, thereby eliminating seams and reducing resistivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conformal fill approach is used to fill via with tungsten, then via filling is achieved, but tungsten grain growth is limited and seams are formed leading to increased resistivity
Solution Approach 1:
A nucleation layer is deposited on the dielectric surface before the main tungsten deposition process. This preliminary action creates a surface that promotes uniform tungsten nucleation and grain growth, preventing seam formation during via filling while maintaining low resistivity
Solution Approach 2:
The nucleation layer acts as an intermediary between the dielectric surface and the tungsten deposit. It mediates the interaction by providing a suitable surface for tungsten nucleation, enabling continuous grain growth without seams and achieving both good via filling and low resistance
2Manufacturing precision
If conformal fill approach is used, then via filling is achieved, but tungsten grain growth is limited due to dimension constraints
Solution Approach 1:
The nucleation layer is prepared in advance to provide a surface that facilitates extended tungsten grain growth. This preliminary preparation allows grains to develop larger sizes within the via dimensions, improving electrical properties while completing the via fill
Solution Approach 2:
The deposition parameters are optimized to enable continuous grain growth mode rather than limited grain growth. By adjusting deposition conditions and using the nucleation layer, the tungsten grains can grow larger within the constrained via dimensions, achieving both complete filling and improved grain structure
3Shape
If longer deposition period is used to allow tungsten grain growth, then grain size increases, but deposition time increases
Solution Approach 1:
The nucleation layer is deposited beforehand to create optimal conditions for rapid tungsten grain growth. This preliminary preparation enables the subsequent deposition to proceed more efficiently, achieving larger grain sizes in reduced time compared to direct deposition on dielectric
Solution Approach 2:
The deposition process is structured in periodic stages: nucleation layer deposition, followed by controlled tungsten deposition with interruptions for in-situ annealing. This periodic approach allows grain growth to proceed efficiently through thermal activation during annealing periods, reducing total deposition time while achieving large grain sizes
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 method achieves improved tungsten grain structure and reduced via resistance by selectively growing tungsten from the contact bottom, allowing for a bottom-up fill of vias and minimizing resistivity, as demonstrated by comparisons with conformal fill approaches.
Implementation Method 1
depositing metal using chemical vapor deposition (CVD) during a first deposition period
Implementation Method 2
depositing metal using physical vapor deposition (PVD)
Implementation Method 3
performing a sputter etch process prior to the first deposition period to at least partially remove the nucleation layer in the via at a contact bottom
Data Source
AI summary
A method for processing a substrate includes providing a substrate including a metal layer, a dielectric layer arranged on the metal layer, and at least one of a via and a trench formed in the dielectric layer; depositing a metal using chemical vapor deposition (CVD) during a first deposition period, wherein the first deposition period is longer than a first nucleation period that is required to deposit the metal on the metal layer; stopping the first deposition period prior to a second nucleation delay period, wherein the second nucleation period is required to deposit the metal on the dielectric layer; performing the depositing and the stopping N times, where N is an integer greater than or equal to one; and after the performing, depositing the metal using CVD during a second deposition period that is longer than the second nucleation delay period.