3D Memory Film Stack With Doped Si Layers Against Substrate Bowing
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Solution Overview
Problem
Three-dimensional memory structures face issues of substrate bowing and deformation due to lattice mismatch between Si and SiGe layers, leading to increased defectivity and reduced performance.
Innovation Solution
A 3D memory structure is formed with a base silicon layer, a silicon germanium layer, and doped silicon layers containing carbon or boron dopants, with controlled dopant concentrations and transition layers to reduce compressive stress and eliminate substrate bowing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If alternate layers of Si and SiGe are grown epitaxially to increase memory density, then memory density is improved, but substrate bowing and deformation occur due to lattice mismatch strain
Solution Approach 1:
A doped silicon layer is introduced as an intermediary layer between the SiGe layer and the substrate. This intermediate layer acts as a stress buffer that absorbs the lattice mismatch strain between Si and SiGe, preventing the strain from propagating to the substrate and causing bowing. The doped silicon layer serves as a mediator that decouples the stress transmission path.
Solution Approach 2:
The invention changes the physical-chemical parameters of the silicon layer by introducing dopants (such as boron or phosphorus) at controlled concentrations. This parameter change modifies the mechanical properties of the silicon layer, enabling it to better accommodate the strain from SiGe while maintaining structural integrity and preventing substrate deformation.
2Quantity of substance
If SiGe layers are used to increase memory density, then memory capacity is improved, but defectivity increases due to strain-induced deformation
Solution Approach 1:
The doped silicon layer serves as a protective intermediary that isolates the SiGe layer from direct interaction with the substrate. By absorbing and distributing the strain energy, this intermediate layer prevents strain-induced dislocations and defects from forming in the SiGe memory layers, thereby maintaining high reliability and low defectivity.
Solution Approach 2:
The doped silicon layer is deposited beforehand to provide a cushioning effect against the incoming strain from subsequent SiGe layers. This preventive measure absorbs the stress before it can cause damage, cushioning the structure against future strain accumulation and defect formation during continued epitaxial growth.
3Strength
If doped silicon layers are added to reduce substrate bowing, then structural integrity is improved, but fabrication complexity increases
Solution Approach 1:
Rather than adding complex structural elements, the invention achieves improved structural integrity by changing the parameters of an existing silicon layer - specifically, by controlling dopant concentration and distribution. This parameter-based approach maintains relative fabrication simplicity while effectively managing stress and improving structural strength.
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 proposed structure reduces substrate bowing and defectivity, maintaining structural integrity and enabling efficient fabrication of 3D memory devices with improved performance.
Implementation Method 1
a doped silicon (Si) layer disposed on at least one side of the SiGe layer, wherein the doped Si layer contains a dopant that is at least one of carbon (C) or boron (B)... reduce or eliminate substrate bowing
Implementation Method 2
In some three-dimensional memory structures, alternate layers of Si and SiGe are grown epitaxially from crystal silicon substrate
Implementation Method 3
there is a strain induced from the mismatch in lattice between Si and Ge which can undesirably result in deformation, or bowing, of the substrate
Data Source
AI summary
Three-dimensional (3D) memory structures and methods of formation of same are provided herein. In some embodiments, a 3D memory fabrication structure includes: a base silicon (Si) layer; a silicon germanium (SiGe) layer disposed above the base Si layer; and a doped silicon (Si) layer disposed on at least one side of the SiGe layer, wherein the doped Si layer contains a dopant that is at least one of carbon (C) or boron (B).