Ru Liner and Oxidized Barrier for Copper Metallization
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Solution Overview
Problem
Current semiconductor manufacturing techniques face challenges in achieving precise thickness and composition control, conformality, and interlayer dielectric damage in back-end-of-line (BEOL) processes, particularly at 10 nm technology nodes, where PVD TaN has reached its limits and ALD barrier layers have not delivered effective Cu interface performance.
Innovation Solution
The integration method involves depositing a conformal barrier layer and a ruthenium (Ru) metal liner on a substrate with a recessed feature, followed by oxidation of the barrier layer, filling with CuMn metal using ionized physical vapor deposition (IPVD), and heat-treating to diffuse Mn and react with the oxidized barrier layer to form a Mn-containing diffusion barrier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If PVD TaN is used for barrier layer deposition, then deposition speed is high, but thickness and composition control precision deteriorates
Solution Approach 1:
The barrier layer deposition process is segmented into multiple stages: initial PVD Ta flash deposition for rapid coverage, followed by ALD TaN deposition for precise thickness and composition control. This segmentation allows each method to operate in its optimal range, combining high productivity with high precision.
Solution Approach 2:
A Ru metal liner is introduced as an intermediary layer between the PVD Ta barrier and the Cu fill. This Ru liner serves as a mediator that improves the barrier-Cu interface properties, enabling better adhesion and preventing Cu diffusion while maintaining the advantages of PVD deposition.
2Manufacturing precision
If ALD barrier layers are used, then conformality is improved, but Cu interface performance deteriorates
Solution Approach 1:
The barrier structure is designed as a composite system combining ALD TaN (providing conformal coverage), PVD Ta (providing robust barrier properties), and Ru metal liner (providing superior Cu interface). This composite approach leverages the strengths of each material to achieve both conformality and Cu interface performance.
Solution Approach 2:
The Ru metal liner acts as an intermediary between the ALD TaN barrier and the Cu fill, improving interfacial properties such as adhesion and diffusion control, thereby enhancing Cu interface performance while preserving the conformal advantages of ALD deposition.
3Productivity
If PVD Cu seed layers are used, then Cu fill is improved, but barrier-Cu interface quality deteriorates
Solution Approach 1:
The Ru metal liner serves as an intermediary layer between the PVD Ta barrier and the PVD Cu seed layer, improving the barrier-Cu interface quality. The Ru layer provides excellent adhesion and prevents direct interaction between Ta and Cu that could form harmful intermetallic compounds, while still enabling effective Cu fill.
Solution Approach 2:
The Ru metal liner is deposited in advance before Cu filling, preparing the interface with optimal properties for Cu adhesion and diffusion control. This preliminary action ensures that when Cu is deposited, the interface is already optimized for both fill quality and long-term reliability.
4Reliability
If barrier layer thickness is increased, then Cu diffusion prevention is improved, but void formation increases
Solution Approach 1:
The barrier structure uses a composite design with thin ALD TaN layer (for conformality and preventing voids), supported by PVD Ta (for robust diffusion prevention), and Ru metal liner (for interface control). This composite approach achieves effective Cu diffusion prevention with minimal thickness, avoiding void formation that would occur with thicker single-layer barriers.
Solution Approach 2:
Different regions of the barrier structure have different thicknesses and compositions optimized for their specific functions: the ALD TaN provides conformal coverage in high-aspect-ratio regions, the PVD Ta provides robust barrier properties in low-aspect-ratio regions, and the Ru liner provides localized interface improvement. This local optimization prevents both over-thickening (causing voids) and under-thickening (allowing diffusion).
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 time-dependent dielectric breakdown (TDDB) and time-zero dielectric breakdown (TZDB) performance by forming TaNMnO or TaAlNMnO barriers, improving barrier properties and reducing void formation and interlayer damage.
Implementation Method 1
exposing the substrate to an oxidation source gas to oxidize the barrier layer through the Ru metal liner
Implementation Method 2
heat-treating the substrate to diffuse Mn from the CuMn metal to the oxidized barrier layer
Implementation Method 3
filling the recessed feature with CuMn metal using an ionized physical vapor deposition (IPVD) process
Data Source
AI summary
Methods for integration of conformal barrier layers and Ru metal liners with Cu metallization in semiconductor manufacturing are described in several embodiments. According to one embodiment, the method includes providing a substrate containing a recessed feature, depositing a barrier layer in the recessed feature, depositing a Ru metal liner on the barrier layer, and exposing the substrate to an oxidation source gas to oxidize the barrier layer through the Ru metal liner. The method further includes filling the recessed feature with CuMn metal using an ionized physical vapor deposition (IPVD) process, heat-treating the substrate to diffuse Mn from the CuMn metal to the oxidized barrier layer, and reacting the diffused Mn with the oxidized barrier layer to form a Mn-containing diffusion barrier.