Capacitor Manufacturing via Overhang Removal
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Solution Overview
Problem
Conventional methods for manufacturing stacked capacitors in deep holes for DRAMs face issues with bowing during dry etching, leading to gaps and poor dielectric coverage, which result in mechanical stress susceptibility and low product yield.
Innovation Solution
A method involving the deposition of interlayer insulating films with different etching rates for wet etching, removing the overhang structure to prevent gap formation and ensure wider hole widths, and using a hard mask to form deep holes with a bowing shape, followed by wet etching to expand the hole diameter without short-circuiting adjacent capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If dry etching is used to form deep holes for stacked capacitors, then the hole depth can be achieved, but bowing occurs leading to gap formation and poor dielectric coverage
Solution Approach 1:
The patent divides the etching process into two distinct stages: first, dry etching is used to create the deep hole structure, and second, wet etching is applied to remove the overhang structure. This segmentation allows each etching method to perform its optimal function without the drawbacks of using a single method for the entire process.
Solution Approach 2:
The patent converts the harmful overhang structure created by dry etching bowing into a beneficial feature. By intentionally forming the overhang structure first and then selectively removing it through wet etching, the process transforms the defect into a controlled intermediate state that enables precise gap prevention while maintaining deep hole formation.
2Length of stationary object
If overhang structure is present in deep holes, then hole depth is maintained, but gap formation occurs reducing mechanical stability
Solution Approach 1:
The patent performs preliminary removal of the overhang structure through wet etching before forming the dielectric layer. This preliminary action prevents gap formation during subsequent processing steps, ensuring mechanical stability is maintained from the outset rather than attempting to correct gaps after dielectric formation.
Solution Approach 2:
The patent introduces wet etching as an intermediary process between dry etching and dielectric formation. This intermediate step selectively removes the overhang structure that would otherwise cause gaps, acting as a mediator that preserves both the deep hole structure and the mechanical stability of the final device.
3Manufacturing precision
If wet etching is used to expand hole diameter, then dielectric coverage is improved, but adjacent capacitors may short-circuit
Solution Approach 1:
The patent applies wet etching with locally differentiated etching rates for different interlayer insulating film materials. The first interlayer insulating film is designed to etch faster than the second film, allowing selective widening of holes in the first film region without compromising the isolation provided by the second film, thus preventing short-circuits between adjacent capacitors.
Solution Approach 2:
The patent changes the etching rate parameter by selecting different wet etching conditions for different interlayer insulating film materials. By controlling the chemical etching rate to be higher for the first film material than for the second film material, the process achieves localized hole expansion where needed while maintaining isolation where required.
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 prevents gap formation and ensures improved dielectric coverage, enhancing the reliability and mechanical stability of the capacitors, thereby improving product yield and reliability.
Implementation Method 1
depositing an interlayer insulating film on or above a plug
Implementation Method 2
depositing an interlayer insulating film on or above a plug
Implementation Method 3
wet etching to expand the hole diameter
Data Source
AI summary
A method for manufacturing a capacitor includes depositing an interlayer insulating film on or above a plug connected to a switching element, forming a hole in the interlayer insulating film such that the opening portion of the hole is surrounded by an overhang structure and that the plug is exposed in the bottom of the hole, removing the overhang structure, forming a lower electrode on the inner surface of the deep hole, forming a dielectric on the lower electrode, and forming an upper electrode on the dielectric. The above steps prevent the formation of a gap in the capacitor, since the overhang structure as a cause of the gap is removed. The coverage by the dielectric is also prevented from being poor.