Ruthenium Hard Mask Interface Layer for Low-Resistivity Memory Devices
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Solution Overview
Problem
Current methods for forming silicon nitride layers on ruthenium layers in memory devices result in increased resistivity and surface roughness due to oxidation and the formation of ruthenium silicide, which are exacerbated by high deposition temperatures and the use of multiple processing chambers, leading to decreased throughput and compromised electrical properties.
Innovation Solution
A plasma treatment is applied to the ruthenium layer to form an interface layer, followed by a plasma-enhanced chemical vapor deposition of the silicon nitride layer, all performed in a single processing chamber, thereby reducing roughness and resistivity by preventing ruthenium silicide formation and maintaining electrical integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two steps are used to deposit silicon nitride layer (ALD followed by PECVD or furnace deposition), then the silicon nitride layer can be formed, but the throughput decreases and additional interfaces are introduced which expedite oxidization of ruthenium layer
Solution Approach 1:
The patent combines the deposition of silicon nitride layer and the formation of interface layer into a single PECVD process step, eliminating the need for separate ALD and PECVD chambers. This merging of operations reduces the number of processing chambers from two to one, thereby increasing throughput while simultaneously reducing the number of interfaces that would otherwise promote ruthenium oxidation.
Solution Approach 2:
The interface layer is formed as a preliminary action within the same PECVD process that deposits the silicon nitride layer. By pre-forming the interface layer with appropriate composition and structure during the same deposition process, the ruthenium layer is protected from oxidation before subsequent high-temperature annealing steps, without requiring additional processing time or chambers.
2Manufacturing precision
If high temperature steps are used during silicon nitride layer formation, then the silicon nitride layer can be deposited, but the resistivity and surface roughness of ruthenium layer increase
Solution Approach 1:
The interface layer acts as an intermediary between the ruthenium layer and the silicon nitride layer. This intermediate layer prevents direct contact and reaction between ruthenium and silicon nitride during high-temperature deposition and annealing processes, thereby preventing ruthenium silicide formation and maintaining the surface roughness and electrical properties of the ruthenium layer even at elevated temperatures.
Solution Approach 2:
The patent converts the potentially harmful effect of high temperature (which causes oxidation and silicide formation) into a beneficial process by using it to form a controlled interface layer within the same PECVD chamber. The interface layer forms in situ during deposition and serves to protect the ruthenium layer during subsequent high-temperature annealing, transforming the harmful thermal exposure into a protective mechanism.
3Reliability
If ALD is used to deposit silicon nitride layer first, then PECVD or furnace deposition is used, but this introduces additional interfaces that increase oxidization of ruthenium layer
Solution Approach 1:
The patent merges the formation of the interface layer and the silicon nitride layer into a single PECVD deposition process. This eliminates the additional interface that would be created by separate ALD and PECVD steps, reducing the total number of interfaces between layers. The single interface formed between the combined layer and the ruthenium layer has optimized composition and structure that provides superior oxidation resistance compared to multiple interfaces.
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 reduced resistivity and surface roughness in the memory device, enhancing its electrical performance and throughput by eliminating the need for additional processing steps and chambers.
Implementation Method 1
pre-treating the ruthenium layer with a plasma to form an interface layer on the ruthenium layer
Implementation Method 2
forming a silicon nitride layer on the interface layer using a plasma-enhanced chemical vapor deposition (PECVD) process
Data Source
AI summary
Memory devices and methods of forming memory devices are described. The memory devices comprise a silicon nitride hard mask layer on a ruthenium layer. Forming the silicon nitride hard mask layer on the ruthenium comprises pre-treating the ruthenium layer with a plasma to form an interface layer on the ruthenium layer; and forming a silicon nitride layer on the interface layer by plasma-enhanced chemical vapor deposition (PECVD). Pre-treating the ruthenium layer, in some embodiments, results in the interface layer having a reduced roughness and the memory device having a reduced resistivity compared to a memory device that does not include the interface layer.