Substrate Etching via Sequential Gas Supply
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Solution Overview
Problem
Existing methods for etching silicon without plasma face challenges in controlling etching rate and shape due to the simultaneous use of multiple etching species like fluorine, nitrogen monoxide, and nitrosyl fluoride, which result in increased etching rates and poor controllability at temperatures below 60°C, leading to agglomerated layers and poor surface quality.
Innovation Solution
A substrate processing method involving a fluorine-based gas supply, followed by a purge gas to discharge excess fluorine, and then a nitrogen-based gas to control the etching process, maintaining the substrate temperature at 60°C or less to prevent simultaneous etching by multiple species, ensuring controlled etching through atomic layer etching (ALE) and maintaining a smooth surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fluorine gas, nitrogen monoxide gas and nitrosyl fluoride gas are simultaneously supplied for etching silicon, then the etching rate is increased, but the controllability of etching rate and shape deteriorates
Solution Approach 1:
The patent segments the simultaneous supply of multiple etching gases into sequential steps: first supplying fluorine-based gas to form silicon fluoride, then supplying nitrogen-based gas to remove the silicon fluoride layer. This temporal segmentation prevents multiple etching species from acting simultaneously, thereby maintaining etching rate while improving controllability of etching shape and surface quality.
2Manufacturing precision
If the temperature of the wafer is lowered below 60°C to improve shape controllability, then the etching rate decreases and agglomerated layers are generated, but the etching efficiency deteriorates
Solution Approach 1:
The patent changes the process parameters by controlling wafer temperature to be 60°C or lower during the etching process. This temperature parameter control prevents the formation of agglomerated layers while maintaining good shape controllability. The sequential gas supply method compensates for the reduced etching rate at lower temperatures, thereby maintaining etching efficiency.
3Productivity
If the temperature of the wafer is raised to 230°C or above to increase etching rate, then the etching speed improves but the shape controllability deteriorates due to surface orientation effects
Solution Approach 1:
By segmenting the etching process into two distinct steps with different gas supplies, the patent achieves effective etching at lower temperatures (60°C or lower) where shape controllability is excellent. This eliminates the need to raise temperature to 230°C or above, thereby avoiding the surface orientation effects that deteriorate shape controllability while still maintaining high etching efficiency through the sequential process.
4Productivity
If multiple etching species are used simultaneously, then the etching capability is enhanced, but the formation of agglomerated layers occurs and surface quality deteriorates
Solution Approach 1:
The patent segments the action of different etching species by supplying fluorine-based gas first to form silicon fluoride, then supplying nitrogen-based gas to remove the layer. This temporal separation prevents multiple etching species from acting simultaneously, eliminating the formation of agglomerated layers and maintaining excellent surface quality while preserving etching capability.
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 allows for precise control of the etching rate and shape of silicon-based films, preventing rough surfaces and ensuring consistent etching by limiting the presence of multiple etching species, thus achieving a desired etching shape and improving controllability at practical temperatures.
Implementation Method 1
a fluorine-based gas supply step of supplying a fluorine-based gas into a processing chamber where a substrate having a silicon-based film is accommodated
Implementation Method 2
a purge gas supply step of supplying a purge gas for discharging the supplied fluorine-based gas into the processing chamber
Implementation Method 3
a nitrogen-based gas supply step of supplying a nitrogen-based gas into the processing chamber from which the fluorine-based gas has been discharged
Data Source
AI summary
A substrate processing method includes a fluorine-based gas supply step of supplying a fluorine-based gas into a processing chamber where a substrate having a silicon-based film is accommodated, a purge gas supply step of supplying a purge gas for discharging the supplied fluorine-based gas into the processing chamber. The substrate processing method further includes a nitrogen-based gas supply step of supplying a nitrogen-based gas into the processing chamber from which the fluorine-based gas has been discharged. In the substrate processing method, at least in the fluorine-based gas supply step and the purge gas supply step, a temperature of the substrate is maintained at 60° C. or less.