DRAM Word Line Protrusion for Simultaneous Through-Hole Etching
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Solution Overview
Problem
The high production cost of Dynamic Random Access Memory (DRAM) is attributed to the need for multiple process steps to form through holes in the peripheral and array regions, which can result in overetching of the active layer or incomplete exposure of the word line conductive layer, affecting the semiconductor structure's performance.
Innovation Solution
A protrusion is formed atop the first word line conductive layer, allowing for simultaneous etching of the first and second through holes, reducing the depth difference and enabling integrated process steps, thereby reducing production costs and improving semiconductor structure performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If separate process steps are used to form first and second through holes, then the depth difference between active layer and first word line conductive layer can be accommodated, but the production cost increases and manufacturing complexity increases
Solution Approach 1:
The patent combines the formation of first through hole (exposing active layer) and second through hole (exposing first word line conductive layer) into a single etching process step. This is achieved by designing the isolation layer thickness to simultaneously expose both the active layer and the protrusion of the first word line conductive layer, eliminating the need for separate process steps and reducing manufacturing complexity while maintaining complete exposure of both structures
2Manufacturing precision
If separate process steps are used to form first and second through holes, then etching control can be improved, but the manufacturing time increases and productivity decreases
Solution Approach 1:
The patent merges two separate etching operations into one unified etching step that forms both first and second through holes simultaneously. The isolation layer is designed with specific thickness to ensure that a single etching process can expose both the active layer and the first word line conductive layer protrusion, thereby reducing manufacturing time and improving productivity while maintaining adequate etching control
3Manufacturing precision
If the isolation layer thickness is increased to expose the first word line conductive layer, then the second through hole formation is improved, but the active layer may be overetched
Solution Approach 1:
The patent applies local quality by creating a protrusion structure of the first word line conductive layer that extends upward. This localized structural modification allows the isolation layer to be etched to a depth that exposes the protrusion without requiring excessive etching that would damage the active layer. The protrusion acts as a local feature that enables selective exposure
4Ease of manufacture
If a protrusion is formed on the first word line conductive layer, then the depth difference is reduced allowing simultaneous through hole formation, but the device structure becomes more complex
Solution Approach 1:
The patent applies preliminary action by forming the protrusion structure of the first word line conductive layer before creating the through holes. This pre-formed protrusion structure facilitates subsequent simultaneous formation of first and second through holes in a single etching step, simplifying the manufacturing process while the protrusion itself is created using standard deposition and patterning techniques
Data Source
AI summary
A semiconductor structure includes a peripheral region and an array region. A substrate is provided. An active layer is provided in the substrate corresponding to the peripheral region. A word line groove is formed in the substrate corresponding to the array region. A word line is formed in the word line groove. The word line includes a first word line conductive layer and a second word line conductive layer with one stacked on another. A top of the first word line conductive layer is a protrusion. The protrusion protrudes along a direction pointing from the first word line conductive layer to the second word line conductive layer. An isolation layer covering the substrate is formed. A first through hole and a second through hole both penetrating through the isolation layer are formed simultaneously. The first through hole exposes the active layer. The second through hole exposes the protrusion.