DRAM Charge Storage Electrode Edge Rounding via Isotropic Etching
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Solution Overview
Problem
The manufacturing of high-capacitance cylindrical capacitors for DRAM memory cells faces challenges due to physical instability, leading to yield decreases and increased leakage current caused by angled portions on the charge storage electrodes, which result from misalignment and variation in photolithography processes during the formation of support films and etching.
Innovation Solution
A method involving the formation of a U-shaped charge storage electrode with a smoothly-curved angled portion, achieved through specific etching processes including isotropic etching to round the edge of the electrode, reducing the angle and preventing electric field focusing, thereby enhancing mechanical support and reducing leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the charge storage electrode is made taller to increase surface area and capacitance, then the capacitance increases, but the physical stability decreases and collapse occurs during manufacturing
Solution Approach 1:
The patent applies local quality by forming a support film with different material properties (silicon nitride) than the capacitor inter-layer film (silicon oxide) specifically in regions where mechanical support is needed. This localized differentiation provides structural reinforcement to the taller charge storage electrode without affecting the overall capacitor design, resolving the contradiction between increased height for capacitance and the need for stability.
2Device complexity
If the photolithography process is used to form the support film and pouring holes, then the manufacturing precision is limited by misalignment and variation, but the manufacturing complexity is reduced
Solution Approach 1:
The patent applies preliminary action by forming the support film before forming the charge storage electrode. This sequence allows the support film to be pre-positioned to provide mechanical reinforcement, and subsequent photolithography steps can proceed with standard precision requirements. The support film acts as a preliminary structural foundation that compensates for later alignment variations in the pouring hole formation process.
3Use of energy by moving object
If the pouring hole diameter is increased to enhance circulation of etching solution and film forming gas, then the mass transport is improved, but the support film area remaining to mechanically support the charge storage electrode is reduced
Solution Approach 1:
The patent applies composite materials by combining silicon oxide (capacitor inter-layer film) and silicon nitride (support film) with different functional properties. The silicon nitride provides mechanical strength while the silicon oxide allows for etching access. This composite structure enables the formation of pouring holes with sufficient diameter for mass transport while the remaining support film maintains adequate mechanical support for the charge storage electrode.
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 method effectively stabilizes the charge storage electrodes, reducing leakage current and improving manufacturing yield by rounding the edge of the charge storage electrodes, thus enhancing the reliability and performance of the capacitors.
Implementation Method 1
A part of the first portion of the electrode is removed by an isotropic etching
Data Source
AI summary
A method of manufacturing a semiconductor device may include, but is not limited to the following processes. A first insulating film is formed over a substrate. A second insulating film is formed on the first insulating film. An electrode penetrating the first and the second insulating films is formed. A part of the second insulating film and a part of the electrode are removed so that a first hole is formed in the second insulating film. A first portion of the electrode is exposed through the first hole. A part of the first portion of the electrode is removed by an isotropic etching.