Molybdenum and Tungsten Etching with Pore Fill Recovery
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Solution Overview
Problem
Current etching methods for molybdenum and tungsten films in semiconductor storage devices face challenges in selectively etching these materials without damaging the underlying silicon-containing structures and in addressing the formation of pits that can adversely affect device performance.
Innovation Solution
An etching method involving the use of oxidation gases like MoF6 and WF6 for initial etching, followed by filling exposed pores with the same materials using reduction gases, and subsequent secondary etching with oxidation gases to ensure precise film formation and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If plasma etching using Cl2 gas, O2 gas, and N2 gas is performed to selectively etch a tungsten film, then the tungsten film can be etched with selectivity against silicon-containing films, but pits may form inside the tungsten film which adversely affect device performance
Solution Approach 1:
The etching process is divided into multiple sequential steps: first etching with Cl2/O2/N2 plasma, then filling exposed pores with WF6 gas, and finally performing a second etching step. This segmentation allows the process to both create the necessary etching selectivity and fill in the harmful pits that form during etching, thereby resolving the contradiction between manufacturing precision and device reliability
Solution Approach 2:
The pits that form as a harmful byproduct of the etching process are converted into a benefit by filling them with tungsten using WF6 gas. The same etching process that creates defects also creates the conditions for targeted material deposition, transforming the harmful pits into filled regions that improve device performance
2Reliability
If the first etching is stopped when pores are exposed to fill them with tungsten, then pits can be filled to improve device reliability, but the overall etching process time increases due to the additional filling and second etching steps
Solution Approach 1:
The etching process uses periodic action by alternating between etching steps and a filling step. The first etching exposes pores, then the process pauses to fill pores with tungsten using WF6 gas, and finally a second etching completes the removal. This periodic alternation allows pit filling without requiring continuous etching, improving reliability while managing process time through efficient cycling
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 allows for high-selectivity etching of molybdenum and tungsten films while filling pits to prevent device damage, ensuring uniform film formation and continuous process operation with minimal impurity inclusion.
Implementation Method 1
performing a first etching on the first film by supplying an oxidation gas and a first gas selected from a MoF6 gas and a WF6 gas into the chamber
Implementation Method 2
filling the pore with one of molybdenum and tungsten by stopping the first etching and supplying a reduction gas and a second gas selected the MoF6 gas and the WF6 gas into the chamber
Data Source
AI summary
An etching method includes: providing, in a chamber, a substrate including a structure including a first film selected from a molybdenum film and a tungsten film; performing a first etching on the first film by supplying an oxidation gas and a first gas selected from a MoF6 gas and a WF6 gas into the chamber; when a pore present inside the first film is exposed by the first etching, filling the pore with one of molybdenum and tungsten by stopping the first etching and supplying a reduction gas and a second gas selected the MoF6 gas and the WF6 gas into the chamber; and performing a second etching on a filling layer formed in the filling and the first film by supplying the oxidation gas and a third gas selected from the MoF6 gas and the WF6 gas into the chamber.