Moisture Scavenging Layer for Thinner Barrier Liner Stacks
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Solution Overview
Problem
Current methods for forming thinner barrier/liner stacks in semiconductor vias and metal lines compromise moisture and oxygen barrier properties, leading to reduced electromigration (EM) reliability.
Innovation Solution
A moisture scavenging layer is formed prior to the barrier/liner stack, using manganese or titanium precursors, which are annealed to create a moisture scavenging layer, allowing for a thinner barrier/liner stack of TaN and Ta or TaN and Co/Ru, reducing moisture concentration and enabling thinner stacks without compromising barrier properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the barrier/liner thickness is reduced to lower via and line resistance, then electrical conductivity improves, but moisture and oxygen barrier properties deteriorate
Solution Approach 1:
The barrier system is segmented into three functional layers: a moisture scavenging layer (Mn or Ti) that actively absorbs moisture, a barrier/liner stack (TaN and Ta or Co/Ru) that provides oxygen and moisture barrier, and a copper layer for conductivity. This segmentation allows each layer to specialize in one function, enabling the barrier/liner stack to be thinner while overall protection is maintained through the scavenging layer's moisture absorption capability
Solution Approach 2:
The moisture scavenging layer acts as an intermediary between the moisture source (ULK dielectric) and the copper via/line. By placing this reactive layer (Mn or Ti) between them, it intercepts and absorbs moisture before it can reach and compromise the barrier/liner stack or copper, enabling the barrier/liner to be thinner while maintaining protection
2Manufacturing precision
If ALD TaN is used instead of PVD TaN for barrier/liner formation, then conformality improves, but density and moisture barrier properties worsen
Solution Approach 1:
The patent uses a composite barrier system combining ALD TaN (providing conformal coverage) with PVD Ta or Co/Ru layers (providing high density and moisture barrier). The ALD TaN layer ensures complete coverage of via sidewalls and bottom, while the PVD layers compensate for the lower density of ALD TaN, together providing both conformality and moisture barrier properties
Solution Approach 2:
The patent changes the deposition parameters and material composition of the barrier stack. By using a bilayer or trilayer structure with different deposition methods (ALD and PVD) and materials (TaN, Ta, Co, Ru), it optimizes both conformality and density parameters simultaneously, overcoming the limitation of using either ALD or PVD TaN alone
3Length of stationary object
If CVD Co or Ru is added to thin the barrier/liner stack, then overall thickness reduces, but moisture barrier capability worsens since CVD Co/Ru is not a moisture barrier
Solution Approach 1:
The moisture scavenging layer (Mn or Ti) provides multi-functionality: it absorbs moisture from the ULK dielectric, protects the barrier/liner stack from moisture exposure, and enables the use of thinner PVD Ta or Co/Ru layers. This multi-functional layer compensates for the poor moisture barrier properties of CVD Co/Ru, allowing thickness reduction while maintaining moisture protection
4Reliability
If single layer MnN or Mn or Mn doped ALD TaN is used to achieve thickness below 15 Å, then via resistance reduces, but oxidation stress reliability worsens
Solution Approach 1:
The patent uses composite structures: either Mn/Ti scavenging layer plus PVD Ta or Co/Ru barrier, or Mn doped ALD TaN plus PVD Ta or Co/Ru barrier. These composite structures provide both low resistance (through thin total thickness) and oxidation stress resistance (through the protective PVD metal layer that forms stable oxides and protects the underlying copper and TaN layers)
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 approach achieves thinner barrier/liner stacks that maintain effective moisture and oxygen barrier properties, thereby improving EM reliability and reducing via and line resistance.
Implementation Method 1
annealing the moisture scavenging layer precursor, forming a moisture scavenging layer
Implementation Method 2
forming a moisture scavenging layer which allows for a thinner barrier/liner stack... reducing moisture concentration
Implementation Method 3
PVD of tantalum (Ta)... PVD TaN must act as the moisture barrier
Implementation Method 4
CVD of cobalt (Co) or ruthenium (Ru)... ALD TaN with CVD Co or Ru can achieve the thinnest and most conformal barrier/liner bilayer stack
Data Source
AI summary
A method of forming a thinner barrier/liner stack for vias and metal lines and the resulting device are disclosed. Embodiments include forming a via through an interlayer dielectric (ILD) and capping layer, down to a first metal layer; forming a moisture scavenging layer precursor over the ILD and on side and bottom surfaces of the via; annealing the moisture scavenging layer precursor, forming a moisture scavenging layer; forming a barrier/liner stack over the moisture scavenging layer; and depositing a second metal layer over the barrier/liner stack and filling the via and trench.