Self-Aligned MRAM Bottom Electrode via Reverse Silicide
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Solution Overview
Problem
Existing MRAM fabrication methods are complicated and result in non-uniform recesses due to the need for timed etch processes to recess metals in the underlying interconnect structure, which can lead to contamination and damage to fragile MTJ stacks.
Innovation Solution
A self-aligned reverse silicide process forms a semiconductor/metal alloy bottom electrode by depositing a semiconductor layer over the interconnect structure and using a low thermal budget anneal to react with the metal, creating a self-aligned and uncontaminated interface for the MTJ stack, eliminating the need for recessing metals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If timed etch processes are used to recess metals in the underlying interconnect structure, then the bottom electrode can be formed to couple to the interconnect structure, but the process results in non-uniform recesses and can lead to contamination and damage to fragile MTJ stacks
Solution Approach 1:
Instead of etching the metal interconnect structure to create a recess for the bottom electrode, the patent inverts the approach by depositing the bottom electrode material conformally over the metal interconnect structure without recessing. This eliminates the harmful timed etch process while achieving proper electrical coupling between the bottom electrode and interconnect structure.
Solution Approach 2:
The patent extracts and eliminates the timed etch process step from the fabrication sequence. By removing this problematic process step entirely, the source of contamination and damage to MTJ stacks is eliminated, while the essential function of electrical coupling is achieved through alternative means (conformal deposition over non-recessed metal).
2Ease of manufacture
If timed etch processes are used to recess metals, then the bottom electrode can be formed, but the fabrication process becomes complicated
Solution Approach 1:
The patent simplifies fabrication by inverting the conventional approach: instead of etching metal recesses first and then depositing electrodes, the method deposits bottom electrode material conformally over the as-formed metal interconnect structures. This eliminates complex timed etch processes and achieves uniform interfaces through the self-aligning nature of conformal deposition.
Solution Approach 2:
The conformal deposition process is self-aligning and automatically forms uniform bottom electrode interfaces without requiring precise timing control or complex process sequencing. The process serves itself by naturally conforming to the underlying metal structure geometry, eliminating the need for operator intervention or complex process control.
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 process results in a uniform and uncontaminated interface for the MTJ stack, reducing fabrication complexity and preventing damage to the underlying structures, while ensuring precise alignment and efficient integration of MTJ stacks with interconnects.
Implementation Method 1
initiating a self-aligned chemical reaction between a metal of the interconnect structure and a portion of the layer of semiconductor material that is over the exposed surface of the interconnect structure
Implementation Method 2
using a low thermal budget anneal to react with the metal
Data Source
AI summary
Embodiments of the invention are directed to a method of forming a bottom electrode of a magnetic tunnel junction (MTJ) storage element. A non-limiting example of the method includes forming the bottom electrode of the MTJ storage element such that the bottom electrode is communicatively coupled to an interconnect structure through an in-situ interface, wherein the in-situ interface includes an interface between a bottom surface of the bottom electrode and a top surface of the interconnect structure. A top surface of the bottom electrode is configured to couple to a bottom end of a MTJ stack, and the bottom electrode includes a semiconductor and metal alloy.