Backside PVD Support Design for Substrate Bowing Control
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Solution Overview
Problem
The increasing density of elements/layers in 3D NAND integrated circuits leads to film stresses due to thermal expansion and plasma non-uniformity, causing substrate bowing and misalignment issues, which are not effectively addressed by current backside deposition methods that reduce strain but lose effectiveness after annealing.
Innovation Solution
A method and apparatus for depositing a backside film layer on a substrate using physical vapor deposition, involving flipping the substrate to expose the backside for film deposition without contacting the active front side, using a sputter target with DC power and a magnetron to achieve strain balancing and high stress retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If film is deposited on the backside of the substrate to reduce strain and substrate bowing, then substrate flatness is improved, but the backside film strain is reduced after annealing process
Solution Approach 1:
The patent changes the deposition method from CVD to PVD (physical vapor deposition), which fundamentally alters the film properties. PVD-deposited films have different stress characteristics and thermal stability compared to CVD films, maintaining higher strain levels after annealing. This parameter change in the deposition process resolves the contradiction by preserving backside film strain while achieving substrate flatness.
Solution Approach 2:
The patent replaces the chemical deposition mechanism (CVD) with a physical deposition mechanism (PVD). This substitution changes how the film is deposited and how it responds to thermal processing. The physical deposition process creates films with different intrinsic stress properties that better maintain strain balance through annealing, thus resolving the contradiction between achieving flatness and maintaining film strain stability.
2Ease of operation
If substrate is flipped to deposit backside film, then access to backside is achieved, but risk of damaging front side film increases
Solution Approach 1:
The patent introduces a shadow mask as an intermediary component during the PVD process. The shadow mask is positioned to block deposition material from reaching the front side of the substrate while allowing deposition on the backside. This intermediary protects the front side film integrity while enabling backside film deposition, resolving the contradiction between operational ease and reliability.
3Adaptability or versatility
If additional sources are added to deposition chamber for backside deposition, then backside film deposition capability is achieved, but device complexity and cost increase
Solution Approach 1:
Instead of adding sources to deposit film from the backside, the patent inverts the approach by flipping the substrate and depositing film on the backside from the top. This inversion eliminates the need for complex additional sources or specially designed chamber configurations, achieving backside deposition capability while reducing device complexity and cost.
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 effectively reduces substrate bowing by maintaining strain balance after annealing, with high stress retention and reduced need for protective layers, enabling efficient and cost-effective backside film deposition.
Implementation Method 1
depositing the backside film layer on the backside of the substrate. The backside film layer is deposited using a method including physical vapor deposition
Implementation Method 2
a magnetron disposed adjacent to the second surface of the sputter target. The magnetron includes an inner pole including an inner plurality of magnets, and an outer pole surrounding the inner pole, the outer pole including an outer plurality of magnets
Implementation Method 3
The backside film layer is formed from sputtering from a sputter target, and the backside film layer is deposited by providing direct current (DC) power to the sputter target
Data Source
AI summary
Embodiments of the present disclosure generally relate to methods and apparatus for backside stress engineering of substrates to combat film stresses and bowing issues. In one embodiment, a method of depositing a film layer on a backside of a substrate is provided. The method includes flipping a substrate at a factory interface so that the backside of the substrate is facing up, and transferring the flipped substrate from the factory interface to a physical vapor deposition chamber to deposit a film layer on the backside of the substrate. In another embodiment, an apparatus for depositing a backside film layer on a backside of a substrate, which includes a substrate supporting surface configured to support the substrate at or near the periphery of the substrate supporting surface without contacting an active region on a front side of the substrate.