ReRAM Etch Stop Metal Nitride for Vertical Bit Line Contact
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Solution Overview
Problem
The insulating etch stop layer, such as a silicon nitride layer, is difficult to etch during the manufacturing of three-dimensional resistive random access memory (ReRAM) devices, leading to incomplete removal and failure in electrical contact between the vertical bit line and the underlying drain region of the vertical select transistor.
Innovation Solution
The insulating etch stop layer is not located over the drain region of the vertical select transistor during etching, and a thick enough metal nitride layer is used as an etch stop structure, eliminating the need for a separate silicon nitride etch stop layer, ensuring reliable electrical contact and protecting dielectric pillar structures during anisotropic etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an insulating etch stop layer (silicon nitride) is used during ReRAM device manufacturing, then the etching process can be controlled, but the etch stop layer is difficult to etch completely, leading to incomplete removal and failure in electrical contact
Solution Approach 1:
The patent removes the insulating etch stop layer (silicon nitride) from overlying the drain region of the vertical select transistor. This extraction eliminates the problematic layer that prevented complete etching, allowing the etch process to proceed through to the drain region without obstruction, thereby ensuring proper electrical contact between the bit line and drain region.
Solution Approach 2:
Instead of using a conventional insulating etch stop layer to control etching, the patent inverts the approach by making the etch stop structure electrically conductive (using metal nitride or polysilicon). This inverted approach maintains etch control functionality while eliminating the electrical contact barrier, as the conductive material can be completely removed to expose the drain region.
2Reliability
If a thick metal nitride layer is used as etch stop structure, then electrical contact is ensured and dielectric pillar structures are protected, but the device structure becomes more complex
Solution Approach 1:
The metal nitride layer serves multiple functions simultaneously: it acts as an etch stop structure to protect dielectric pillar structures during anisotropic etching, provides electrical conductivity to ensure proper contact, and can be completely removed when needed. This multi-functionality consolidates what would otherwise require separate components, actually reducing overall device complexity while improving reliability.
Solution Approach 2:
The patent employs composite material structures where metal nitride or polysilicon replaces the conventional silicon nitride etch stop layer. These composite materials combine the etch stop functionality with electrical conductivity, creating a unified structure that performs multiple roles and simplifies the overall device architecture by eliminating the need for separate conductive and insulating layers in the etch stop region.
Data Source
AI summary
A three dimensional ReRAM device includes an etch stop dielectric material layer overlying top surfaces of the dielectric rail structures and the dielectric pillar structures. The etch stop dielectric material layer includes openings in areas that overlie semiconductor pillars of the vertical select transistors. An array of metal nitride portions is located within the openings in the etch stop dielectric material layer. The etch stop dielectric material layer protects the underlying dielectric pillar structures during anisotropic etching steps without covering the metal nitride portions.