Backside Coating for Wafer Bow in 3D Memory Fabrication
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Solution Overview
Problem
The increasing density of 3D memory devices, such as 3D NAND, leads to substrate bow or warpage, causing handling challenges, poor process uniformity, and potential damage due to uncontrolled parasitic local discharges, which existing technologies have not effectively addressed.
Innovation Solution
A method and apparatus that involve depositing a backside coating on the second major surface of a substrate with a film stack to counteract the stresses causing bow or warpage, using a backside processing chamber that can perform deposition and etching without flipping the substrate, thereby minimizing handling and damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high density memory device fabrication is performed with increased layer stacking, then device density is improved, but substrate bow or warpage occurs causing handling challenges and process uniformity issues
Solution Approach 1:
A backside coating is deposited on the substrate before subsequent processing steps to preemptively counteract the bowing effect that will be induced by the film stack. This preliminary action prevents substrate warpage from developing, maintaining substrate flatness throughout the fabrication process while enabling high density device construction
Solution Approach 2:
The stress state of the substrate is modified by depositing a coating with specific stress characteristics on the backside. By changing the physical parameter of substrate stress through the backside coating, the substrate flatness is maintained despite the increasing layer stacking density
2Quantity of substance
If substrate bow is allowed to occur during high density fabrication, then device density is improved, but arcing and parasitic local discharges damage process kits and reduce reliability
Solution Approach 1:
The backside coating is applied in advance to prevent substrate bowing that would otherwise lead to arcing and parasitic discharges. By preemptively counteracting the bowing stress, the reliability of subsequent processing steps is protected while maintaining high device density
3Manufacturing precision
If substrate bow is corrected by flipping and re-coating the substrate, then substrate flatness is improved, but handling complexity and potential damage increase
Solution Approach 1:
Instead of flipping the substrate to coat the bowed surface, the coating is applied to the backside (opposite side) of the substrate. This inverted approach allows the coating to counteract bowing stresses without requiring substrate flipping, thereby maintaining substrate flatness while simplifying handling and reducing damage risk
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 effectively flattens the substrate, reduces patterning overlay errors, and eliminates both out-of-plane and in-plane distortions, enhancing yield and process reliability by relieving stress induced by the memory film stack.
Implementation Method 1
forming a coating a second major surface of the substrate, wherein the coating is configured to counter stresses produced by the film stack and flattens the substrate from the bowed orientation
Data Source
AI summary
A method and apparatus for forming a backside coating on a substrate to counteract stresses from a previously deposited film is disclosed. In one embodiment, a method for flattening a bowed substrate includes providing a substrate having a film stack formed on a first major surface thereof, wherein the substrate comprises a bowed orientation, and forming a coating a second major surface of the substrate, wherein the coating is configured to counter stresses produced by the film stack and flattens the substrate from the bowed orientation.