DRAM Capacitor Electrode Layout for Overlay Alignment
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Solution Overview
Problem
The challenge in semiconductor manufacturing is achieving precise alignment between transistors and capacitors in DRAM cells to prevent increased resistance and reduced charge storage and retrieval effectiveness due to misalignment or deviation in overlay.
Innovation Solution
A semiconductor device with a transistor and capacitor configuration featuring an isolating spacer layer between them, formed using plasma enhanced chemical vapor deposition (PECVD) at lower temperatures, allowing for controlled etching with wet etchants to create larger capacitor openings, enhancing alignment without additional process steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional deposition methods are used to form isolating spacer layers, then higher temperature processing is required, but this increases manufacturing complexity and reduces alignment precision
Solution Approach 1:
The patent changes the deposition temperature parameter from conventional high temperature to lower temperature range, enabling the formation of isolating spacer layers with boron doping that can be selectively etched without requiring additional high-temperature process steps. This parameter change resolves the contradiction by achieving better alignment precision through controlled etching while avoiding the complexity of multiple high-temperature processing stages.
Solution Approach 2:
The patent employs composite material structure by incorporating boron-doped silicon nitride in the isolating spacer layer formed by PECVD. This composite approach allows the layer to serve dual purposes: providing electrical isolation and enabling selective chemical etching. The boron doping creates a material with differentiated etch rates that can be removed selectively to form precise capacitor openings, thereby improving alignment precision without adding process complexity.
2Manufacturing precision
If larger capacitor openings are formed to improve alignment, then charge storage capacity may be reduced, but precise alignment is achieved
Solution Approach 1:
The patent applies preliminary action by forming the isolating spacer layer with predetermined boron doping concentration and thickness before capacitor formation. This pre-configured layer enables controlled selective etching that defines the capacitor opening size. The preliminary preparation of the spacer layer with specific etch characteristics allows precise alignment to be achieved while the etching process itself controls the final opening dimensions, preventing excessive removal that would compromise charge storage capacity.
Solution Approach 2:
The patent utilizes parameter changes in the etching process by controlling the etchant concentration, temperature, and exposure time to achieve selective removal of the boron-doped isolating spacer layer. By precisely controlling these parameters, the capacitor openings are formed with optimal dimensions that ensure both accurate alignment and sufficient charge storage capacity, resolving the contradiction between alignment precision and charge storage effectiveness.
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 configuration improves manufacturing yield, device performance, and reliability by ensuring better alignment between transistors and capacitors, particularly in 3D semiconductor devices.
Implementation Method 1
formed using plasma enhanced chemical vapor deposition (PECVD) at lower temperatures
Implementation Method 2
allowing for controlled etching with wet etchants to create larger capacitor openings
Data Source
AI summary
Systems, devices, and methods for managing capacitor overlay in a semiconductor device are provided. In one aspect, a semiconductor device includes a transistor having a semiconductor body extending along a first direction and a gate structure adjacent to the semiconductor body. A capacitor is coupled to the transistor. The capacitor extends along the first direction and includes a first electrode, a second electrode, and a dielectric structure. An isolating spacer layer is between the transistor and the capacitor along the first direction. The first electrode includes a first portion extending between two ends of the isolating spacer layer along the first direction, and a second portion extending from the first portion along the first direction away from the transistor. A width of the first portion along a second direction perpendicular to the first direction is greater than an outer dimension of the second portion along the second direction.