Tungsten Gate Formation via Nitride Barrier and Sacrificial Etching
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Solution Overview
Problem
In semiconductor memory devices, the dual structure of polysilicon and tungsten silicide films faces challenges in securing resistance and reducing intra-capacitance and inter-gate interference, leading to reliability issues and degraded performance due to tungsten oxidation and misalignment during the Reactive Ion Etching method, and the damascene method struggles with gap-fill characteristics in narrow trenches.
Innovation Solution
A method involving the formation of gate oxide, polysilicon, and nitride films, followed by patterning and spacer formation, with a sacrifice nitride film and insulation film to expose the nitride film, allowing for improved tungsten gate deposition and reduced exposure to high temperatures, enhancing coupling ratio and gap-fill characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the dual structure of polysilicon film and tungsten silicide film is used for control gate, then the conduction function is achieved, but gate resistance cannot be secured and intra-capacitance increases
Solution Approach 1:
The patent changes the material composition of the control gate from the conventional polysilicon/tungsten silicide dual structure to a tungsten nitride/tungsten dual structure. This parameter change in material composition enables achieving lower gate resistance (improved reliability) while maintaining acceptable intra-capacitance levels, resolving the technical contradiction between these two parameters.
2Ease of manufacture
If RIE method is used to etch the gate, then the gate structure is formed, but tungsten oxidization occurs and reliability degrades
Solution Approach 1:
The patent introduces a tungsten nitride film as an intermediary barrier layer between the tungsten film and the environment. This tungsten nitride layer prevents oxidization of the tungsten film during and after the RIE etching process, thereby maintaining gate reliability while still allowing the RIE method to be used for gate formation.
Solution Approach 2:
The patent applies a preliminary protective action by forming the tungsten nitride barrier film before the RIE etching process. This preliminary barrier prevents tungsten oxidization that would otherwise occur during the etching process, ensuring gate reliability is maintained throughout manufacturing.
3Reliability
If damascene method is used to form gate, then RIE method issues are avoided, but misalignment occurs and coupling ratio reduces
Solution Approach 1:
The patent inverts the conventional damascene approach by using the tungsten nitride/tungsten structure with RIE etching instead of the traditional damascene method. This inversion allows maintaining high alignment precision (improved manufacturing precision) while the tungsten nitride barrier prevents oxidization (maintained reliability), resolving the contradiction between these two parameters.
4Productivity
If trench width reduces for higher integration, then device density increases, but W film gap-fill characteristic degrades
Solution Approach 1:
The patent changes the material parameters of the barrier film from tungsten silicide to tungsten nitride, and uses a tungsten nitride/tungsten dual structure. This parameter change in material composition and structure enables the tungsten film to maintain excellent gap-fill characteristics even in narrow trenches, allowing higher device integration density without sacrificing manufacturing precision.
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 method reduces gate resistance and inter-gate interference, improves operation speed, and prevents tungsten oxidation, resulting in enhanced reliability and uniform tungsten gate formation with reduced voltage requirements.
Implementation Method 1
thereafter, the nitride film is removed by being dipped out into a phosphoric acid solution
Implementation Method 2
forming a barrier film and a W film
Data Source
AI summary
Disclosed herein is a method of manufacturing semiconductor devices. The method includes the steps of forming a gate oxide film, a polysilicon film and a nitride film on a semiconductor substrate, and patterning the gate oxide film, the polysilicon film and the nitride film to form poly gates, forming a spacer at the side of the poly gate, forming a sacrifice nitride film on the entire surface, and then forming an interlayer insulation film on the entire surface, polishing the sacrifice nitride film formed on the interlayer insulation film and the poly gates so that the nitride film is exposed, removing top portions of the sacrifice nitride film while removing the nitride film, forming an insulation film spacer at the side exposed through removal of the nitride film, and filling a portion from which the sacrifice oxide film is removed with an insulation film, and forming the tungsten gates in portions from which the nitride films are moved.