Backside PVD Chamber Layout for Wafer Bow Stress Balancing
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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 current backside deposition methods fail to adequately address, especially after annealing processes.
Innovation Solution
A method and apparatus for depositing a backside film layer on a substrate using physical vapor deposition (PVD) in a cluster tool, where the substrate is flipped 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
1Ease of manufacture
If substrate flipping is performed to deposit backside film, then film deposition on backside is enabled, but risk of damaging front side active region increases
Solution Approach 1:
A shadow mask is introduced as an intermediary component between the sputter target and the substrate. The shadow mask selectively blocks deposition material from reaching the front side active region while allowing deposition on the backside, thus enabling backside film formation without damaging the front side patterns
Solution Approach 2:
The substrate is flipped 180 degrees to expose the backside surface to the sputter target. This dimensional change in substrate orientation allows the deposition source to access the backside surface directly, enabling stress compensation film formation without requiring complex lateral positioning
2Ease of manufacture
If additional sources are added to chamber for deposition from below, then backside film deposition is enabled, but chamber cost and complexity increase
Solution Approach 1:
Instead of adding complex below-chamber sources to deposit from underneath, the invention inverts the approach by flipping the substrate and using a conventional top-side sputter target. This inversion simplifies the chamber structure while achieving the same backside deposition goal
Solution Approach 2:
A standard sputter target and deposition chamber are used for both front side and backside film deposition by simply flipping the substrate. This multi-functional use of existing equipment eliminates the need for specialized below-chamber sources and reduces overall system complexity
3Reliability
If protective layer is grown on top of deposited film for flipping, then front side protection is achieved, but process steps and cost increase
Solution Approach 1:
The substrate is flipped to expose the backside surface before deposition begins, and a shadow mask is positioned to protect the front side active region from deposition material. This preliminary protective arrangement eliminates the need for subsequent protective layer deposition and removal steps
Solution Approach 2:
The shadow mask serves as a protective intermediary that blocks deposition material from reaching the front side active region during backside deposition, eliminating the need for additional protective organic layers and their subsequent removal processes
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 PVD-based backside film deposition effectively reduces substrate bowing and maintains strain balance after annealing, providing radial uniform stress with high retention, reducing the need for protective layers and minimizing processing costs and complexity.
Implementation Method 1
The backside film layer is deposited using a method including physical vapor deposition
Implementation Method 2
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
Implementation Method 3
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
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.