Silicon Wafer Orientation for Multilayer Film Warp Reduction
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Solution Overview
Problem
Existing semiconductor device manufacturing methods fail to effectively address warpage issues in silicon wafers during the production of 3DNAND flash memory, particularly due to varying film stress and lack of criteria for specification changes, leading to processing difficulties.
Innovation Solution
The use of silicon wafers with specific crystal orientations, such as (111) for bowl-shaped warpage and (110) for saddle-shaped warpage, combined with optimized oxygen concentration to enhance Young's modulus and reduce warpage, along with a processing method that aligns notch orientations with warp directions to mitigate film stress-induced warping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of laminated films is increased to achieve higher storage capacity in 3DNAND, then the storage capacity increases, but the film stress enormously increases causing significant warpage of the silicon wafer
Solution Approach 1:
The patent changes the crystal orientation parameter of the silicon wafer from conventional orientations to specific orientations ((110) with <100><100> or (100) with <110><110> in-plane orientations). This parameter change in crystal structure fundamentally alters the stress distribution characteristics, enabling the wafer to accommodate the enormously increased film stress from multiple laminated films while maintaining flatness and reducing warpage.
2Shape
If the thickness of the silicon wafer is increased to reduce warpage, then the warpage resistance improves, but the standard thickness is already substantially equal to the calculated required thickness, leaving no room for increase
Solution Approach 1:
Instead of changing the thickness parameter, the patent changes the crystal orientation parameter of the silicon wafer. This alternative parameter change achieves warpage resistance through the unique stress distribution properties of specific crystal orientations, eliminating the need to increase wafer thickness beyond the standard 775 μm.
3Ease of manufacture
If conventional silicon wafer orientations are used, then the manufacturing process is simple, but the film stress causes large warpage that prevents subsequent processing
Solution Approach 1:
The patent modifies the crystal orientation parameter of the silicon wafer to specific orientations ((110) with <100><100> or (100) with <110><110>). This parameter change creates a unique stress distribution pattern that accommodates film stress without causing large warpage, thereby enabling subsequent processing steps to be performed properly while maintaining manufacturing feasibility.
4Quantity of substance
If the number of wiring layers is set to 500 in a 12-inch silicon wafer, then the storage capacity increases, but the required thickness according to conventional formulas is substantially equal to the standard thickness, making it impossible to suppress warping
Solution Approach 1:
The patent changes the crystal orientation parameter of the silicon wafer to specific orientations that fundamentally alter the stress distribution characteristics. This parameter change enables the wafer to accommodate the film stress from 500 wiring layers while maintaining flatness, achieving warp suppression without requiring thickness increase beyond the standard 775 μm.
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 reduces warpage in silicon wafers during device processing, allowing for smooth continuation of subsequent processes without the limitations imposed by large warpage, thereby ensuring successful device manufacturing.
Implementation Method 1
optimized oxygen concentration to enhance Young's modulus and reduce warpage
Data Source
AI summary
A method of reducing warp imparted to a silicon wafer having a (110) plane orientation and a <111> notch orientation by anisotropic film stress of a multilayer film that is to be formed on a surface of the silicon wafer, that includes forming the multilayer film on a surface of the silicon wafer in an orientation so that a direction in which the warp of the wafer will be greatest coincides with a direction in which Young's modulus of a crystal orientation of the silicon wafer is greatest. Also, a method of reducing warp imparted to a silicon wafer having a (111) plane orientation by isotropic film stress of a multilayer film to be formed on a surface of the silicon wafer, that includes, prior to forming the multilayer film, causing the silicon wafer to have an oxygen concentration of 8.0×1017 atoms/cm3 or more (ASTM F-121, 1979).