Composite Silicon Nitride Capping for Copper Interconnects
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional copper (Cu) interconnect technology in semiconductor devices faces issues with charge loss, electromigration, and poor adhesion of silicon nitride capping layers, particularly in deep sub-micron flash memory devices, due to high Si—H bonding and inadequate adhesion during chemical mechanical polishing.
Innovation Solution
A method involving the deposition of a first silicon nitride layer with a high Si—H concentration for improved adhesion, followed by a second silicon nitride layer with a low Si—H concentration to reduce charge loss, using PECVD and adjusting deposition conditions such as SiH4 flow rate and RF power, to form a composite capping layer that enhances electromigration and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single silicon nitride capping layer is deposited by PECVD, then the deposition process is simple, but the layer exhibits poor adhesion to Cu surface and high charge loss due to high Si-H bonding
Solution Approach 1:
The single silicon nitride capping layer is divided into two distinct layers: a first silicon nitride layer deposited by PECVD with controlled Si-H bonding for adhesion, and a second silicon nitride layer deposited by LPCVD with low Si-H bonding for charge retention. This segmentation allows each layer to perform its specific function optimally.
Solution Approach 2:
The patent creates a composite capping structure using two different silicon nitride layers with distinct deposition methods and properties. The first layer (PECVD) provides adhesion to Cu, while the second layer (LPCVD) provides charge retention, forming a composite barrier system that overcomes the limitations of a single material layer.
2Productivity
If PECVD silicon nitride is used as capping layer, then deposition is efficient, but the layer peels during CMP and subsequent processing due to poor adhesion
Solution Approach 1:
The capping structure is segmented into two layers where the first PECVD silicon nitride layer serves as an adhesion promoter that bonds to Cu, while the second LPCVD silicon nitride layer provides structural integrity during CMP. This segmentation prevents peeling by distributing functional requirements across layers.
Solution Approach 2:
The first silicon nitride layer acts as an intermediary between the Cu interconnect and the second silicon nitride layer. It provides the adhesion function that prevents peeling during CMP, while allowing the second layer to maintain its low Si-H bonding characteristics for charge retention.
3Device complexity
If conventional single-layer silicon nitride capping is used, then process complexity is low, but electromigration resistance is poor due to inadequate encapsulation
Solution Approach 1:
The encapsulation structure is segmented into two silicon nitride layers with different deposition characteristics. The first layer ensures complete coverage and adhesion to Cu, while the second layer provides a low-SiH barrier that prevents charge loss, together achieving superior electromigration resistance.
Solution Approach 2:
The patent employs a composite two-layer silicon nitride structure where each layer contributes different properties: the first layer provides adhesion and complete encapsulation, while the second layer provides charge retention. This composite approach achieves better electromigration resistance than a single layer.
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 solution effectively reduces charge loss and improves electromigration performance by ensuring better adhesion of the capping layer to Cu, leading to enhanced data retention and reliability in semiconductor memory devices.
Implementation Method 1
conventional practices comprise forming a damascene opening in an interlayer dielectric, depositing a barrier layer, such as TaN, lining the opening and on the surface of the interlayer dielectric, filling the opening with Cu or a Cu alloy layer, implementing CMP, and forming a silicon nitride capping (diffusion barrier) layer on the exposed surface of the Cu or Cu alloy
Implementation Method 2
A method involving the deposition of a first silicon nitride layer with a high Si—H concentration for improved adhesion, followed by a second silicon nitride layer with a low Si—H concentration to reduce charge loss, using PECVD and adjusting deposition conditions such as SiH4 flow rate and RF power
Data Source
AI summary
Cu interconnects are formed with composite capping layers for reduced electromigration, improved adhesion between Cu and the capping layer, and reduced charge loss in associated non-volatile transistors. Embodiments include depositing a first relatively thin silicon nitride layer having a relatively high concentration of Si—H bonds on the upper surface of a layer of Cu for improved adhesion and reduced electromigration, and depositing a second relatively thick silicon nitride layer having a relatively low concentration of Si—H bonds on the first silicon nitride layer for reduced charge loss.