Hardmask Lateral Etching via Fluorocarbon Plasma
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Solution Overview
Problem
In semiconductor fabrication, hardmasks with critical dimensions (CD) that are too large often render substrates unusable, leading to significant wafer loss, as existing techniques lack effective methods for correcting or tuning CD values without scrapping the wafers.
Innovation Solution
A method for laterally etching dielectric hardmasks using a fluorocarbon mixture in plasma processing, controlling the C/F atomic ratio and electrode bias to precisely trim the hardmask dimensions, allowing for independent control of outgoing CD without adjusting lithography or Hard Mask Opening processes, thereby preventing wafer scrapping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If photolithography and hardmask opening processes are used to create patterns, then features can be transferred into underlying layers, but the critical dimension (CD) of hardmask lines may become too large, rendering substrates unusable
Solution Approach 1:
The patent changes the chemical parameters of the plasma etching process by adjusting the C/F atomic ratio through controlled addition of fluorocarbon gas. This parameter change enables precise tuning of the hardmask CD, allowing correction of oversized features without scrapping wafers, thus resolving the contradiction between manufacturing precision and wafer loss
Solution Approach 2:
The patent replaces mechanical/lithographic CD control methods with plasma chemical etching control. By using plasma chemistry (C/F ratio control) instead of relying solely on lithography parameters, the process achieves post-lithography CD adjustment capability, eliminating wafer scrapping for CD corrections
2Manufacturing precision
If lithography and Hard Mask Opening processes are adjusted to control outgoing CD, then precise CD control can be achieved, but process optimization becomes complex and development time increases
Solution Approach 1:
The patent segments the CD control function from the lithography process into a separate plasma etching step. By isolating the CD trimming function in the plasma process with controlled C/F ratio, the complexity of process optimization is reduced to a single controllable parameter (C/F ratio) rather than coordinating multiple lithography and etching parameters
Solution Approach 2:
The patent introduces plasma chemistry (fluorocarbon addition controlling C/F ratio) as an intermediary mechanism between lithography and final CD outcome. This intermediary provides a dedicated control layer for CD adjustment, simplifying the overall process optimization by creating a clear cause-effect relationship between plasma parameters and CD results
3Loss of substance
If conventional etching processes are used without mask trimming capability, then substrates with oversized hardmask CD must be scrapped, but implementing mask trimming requires additional process steps
Solution Approach 1:
The patent makes the plasma etching process universal by enabling it to perform both the primary etching function and the mask trimming function through a single process step. By controlling the C/F ratio, the same plasma process that etches the underlying layer also laterally etches the hardmask sidewalls, eliminating the need for separate trimming steps while preventing wafer scrapping
Solution Approach 2:
The patent merges the mask trimming function with the main etching process. Instead of using separate process steps for etching and trimming, the plasma chemistry is designed to simultaneously achieve both functions, reducing process complexity while eliminating wafer loss from oversized CDs
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 enables the reduction of hardmask dimensions by up to 6 nm, allowing substrates with initially oversized features to meet specified CD requirements, simplifying process optimization and reducing development time, and providing an all-in-one solution for dielectric-Si stack etching.
Implementation Method 1
A plasma is formed from the etching process gas and the passivating process gas such that the substrate is exposed to the plasma
Implementation Method 2
controlling electrode bias in the plasma processing system
Implementation Method 3
Changing carbon to fluorine (C/F) atomic ratio in processing plasmas enables protective polymer thickness control on dielectric mask sidewalls
Data Source
AI summary
Techniques herein include methods for controllable lateral etching of dielectrics in polymerizing fluorocarbon plasmas. Methods can include dielectric stack etching that uses a mask trimming step as part of a silicon etching process. Using a fluorocarbon mixture for dielectric mask trimming provides several advantages, such as being straightforward to apply and providing additional flexibility to the process flow. Thus, techniques herein provide a method to correct or tune CDs on a hardmask. In general, this technique can include using a fluorine-based and a fluorocarbon-based, or fluorohydrocarbon-based, chemistry for creating a plasma, and controlling a ratio of the two chemistries. Without the hardmask trim method disclosed herein, if a hardmask CD is not on target, then a wafer is scrapped. With hard-mask trim capability in silicon etch as disclosed herein, a given CD can be re-targeted to eliminate wafer-scraps.