Etching Method for Silicon Layers with Metal Mask
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In the etching of silicon-containing layers with a metal-containing mask, there is a challenge in achieving in-plane uniformity of the selection ratio, as the etching rate varies significantly between the edge and central areas of the workpiece, leading to non-uniform consumption of fluorine and mask erosion.
Innovation Solution
A method involving the formation of a fluorocarbon-containing deposit on the mask and focus ring using plasma of a fluorocarbon gas, followed by etching with inert gas plasma radicals, which protects the mask and ensures uniform fluorine consumption across the workpiece surface, thereby enhancing in-plane uniformity of the selection ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If plasma of fluorocarbon gas is used to etch the silicon-containing layer, then the etching process can proceed, but the etching rate varies significantly between edge and central areas, resulting in poor in-plane uniformity
Solution Approach 1:
A fluorocarbon-containing deposit is formed on the mask and focus ring before the etching process. This preliminary deposition modifies the surface properties and creates a more uniform fluorine distribution across the workpiece surface, which subsequently enables uniform etching rates between edge and central areas.
Solution Approach 2:
The fluorocarbon-containing deposit acts as an intermediary layer between the plasma and the silicon-containing layer. This intermediate layer moderates the fluorine distribution and interaction, preventing the non-uniform etching that occurs when plasma directly contacts the silicon layer without the deposit modification.
2Device complexity
If conventional plasma etching is used, then the etching process is simple, but the mask experiences erosion due to non-uniform fluorine consumption
Solution Approach 1:
The fluorocarbon-containing deposit is formed on the mask before etching to create a protective layer. This preliminary action reduces fluorine consumption variability and protects the mask from erosion during the etching process, improving mask reliability without significantly complicating the overall process.
Solution Approach 2:
The fluorocarbon-containing deposit creates a more inert environment around the mask by controlling fluorine release. This inert-like protective layer reduces the aggressive interaction between fluorine and the mask, thereby suppressing mask erosion while maintaining process simplicity.
3Device complexity
If no focus ring is used, then the device structure is simpler, but the in-plane uniformity of etching is poor
Solution Approach 1:
The fluorocarbon-containing deposit is preliminarily formed on the focus ring to enhance its effectiveness. This preliminary deposition ensures that the focus ring can properly control fluorine distribution across the workpiece surface, achieving good in-plane uniformity while maintaining the simplicity of using a standard focus ring structure.
Solution Approach 2:
The formation of the fluorocarbon-containing deposit changes the surface parameters of the focus ring, improving its ability to distribute fluorine uniformly. This parameter change enhances the focus ring's performance in achieving in-plane uniformity without requiring changes to the device structure itself.
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 effectively reduces the difference in etching rates between the edge and central areas, suppresses mask erosion, and maintains uniformity in the etching process, improving the overall in-plane uniformity of the selection ratio.
Implementation Method 1
forming a fluorocarbon-containing deposit on the mask, the silicon-containing layer, and the focus ring by plasma of a fluorocarbon gas
Implementation Method 2
etching the silicon-containing layer using fluorocarbon radicals generated by exposing the deposit to plasma of an inert gas
Data Source
AI summary
Disclosed is a method for etching an etching target layer which contains silicon and is provided with a metal-containing mask thereon. The method includes: generating plasma of a first processing gas containing a fluorocarbon gas in a processing container that accommodates the etching target layer and the mask to form a fluorocarbon-containing deposit on the mask and the etching target layer; and generating plasma of a second processing gas containing an inert gas in the processing container to etch the etching target layer by radicals of the fluorocarbon contained in the deposit. A plurality of sequences, each including the generating the plasma of the first processing gas and the generating the plasma of the second processing gas, are performed.