Hafnium Alloy Floating Gate for NAND Flash Charge Retention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
As NAND flash memory is downscaled, the charge retention characteristics of the floating gate electrode degrade, and existing solutions to improve these characteristics are inadequate.
Innovation Solution
A semiconductor memory device is manufactured using a hafnium alloy-containing film with a ruthenium alloy, where the hafnium and oxygen are deposited using atomic layer deposition and heat treatment to form a hafnium oxide film with a higher hafnium-to-oxygen ratio, stabilizing the ruthenium and preventing its diffusion into the hafnium oxide, thereby enhancing the barrier between the alloy film and the hafnium oxide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If NAND flash memory is downscaled, then device size is reduced, but charge retention characteristics of the floating gate electrode degrade
Solution Approach 1:
The patent changes the material composition parameters of the floating gate electrode by forming a hafnium alloy-containing film with specific metal elements (Ru, Rh, Pd, Os, Ir, Pt) combined with hafnium. This material parameter change increases the bandgap between the floating gate electrode and the insulating film, thereby improving charge retention characteristics despite device downsaling
Solution Approach 2:
The patent uses composite materials by combining hafnium with other metal elements to form a hafnium alloy-containing film. This composite structure provides both the desired electrical characteristics for charge retention and compatibility with the insulating film, resolving the contradiction between device scaling and charge retention
2Reliability
If the upper portion of the floating gate electrode is formed from metal to increase bandgap, then charge retention characteristics improve, but manufacturing complexity increases
Solution Approach 1:
The patent merges the formation of the metal film and hafnium oxide film into a single heat treatment step where both layers are simultaneously heated to form the hafnium alloy-containing film. This combines multiple manufacturing steps into one, reducing process complexity while achieving the desired material composition for improved charge retention
Solution Approach 2:
The patent uses oxygen as an intermediary element that diffuses during heat treatment to facilitate the formation of the hafnium alloy-containing film. The oxygen acts as a mediator that enables the chemical reaction between the metal film and hafnium oxide, simplifying the overall manufacturing process while achieving the desired material properties
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 improves charge retention characteristics by forming a stable barrier that prevents electron leakage and maintains the integrity of the floating gate electrode, even when the memory device is downscaled.
Implementation Method 1
depositing hafnium and oxygen on the metal film
Implementation Method 2
alloying the metal and the hafnium by performing heat treatment
Implementation Method 3
preventing its diffusion into the hafnium oxide, thereby enhancing the barrier between the alloy film and the hafnium oxide
Data Source
AI summary
A semiconductor memory device according to an embodiment, includes a semiconductor substrate, a first insulating film provided on the semiconductor substrate, a silicon film including silicon provided on the first insulating film, a second insulating film provided on the silicon film, a hafnium alloy-containing film provided on the second insulating film, the hafnium alloy-containing film including oxygen and an alloy of hafnium and a metal other than hafnium, a third insulating film provided on the hafnium alloy-containing film, and an electrode provided on the third insulating film.