Tantalum Nitride Etching with Self-Limiting Reaction Layer Cycles
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Solution Overview
Problem
Existing plasma etching techniques for tantalum nitride films suffer from nonuniform etching distribution, leading to reduced yield and accuracy in semiconductor device manufacturing, particularly in fine three-dimensional structures where etching rate varies between the top and bottom of patterns.
Innovation Solution
An etching method involving the formation of a self-saturating surface reaction layer on the tantalum nitride film using reactive particles containing fluorine and hydrogen, followed by removal of this layer through heating, allowing for precise control of etching amount at an atomic layer level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If continuous plasma etching is used to etch tantalum nitride film, then etching speed is maintained, but etching amount becomes nonuniform in wafer in-plane direction and pattern depth direction
Solution Approach 1:
The continuous plasma etching process is segmented into multiple discrete cycles, where each cycle consists of a plasma treatment step followed by a heating step. This segmentation allows the etching process to be divided into controllable stages, enabling uniform etching across the wafer surface and pattern depth while maintaining overall etching speed.
Solution Approach 2:
The etching process employs periodic action by repeating alternating plasma treatment and heating steps in cycles. This periodic alternation between reactive particle supply and thermal treatment ensures uniform etching progression throughout the pattern depth and across the wafer, preventing the nonuniformity that occurs in continuous etching.
2Manufacturing precision
If plasma etching is used to achieve high aspect ratio pattern etching, then processing capability is improved, but pattern collapse occurs due to surface tension of rinse liquid
Solution Approach 1:
The mechanical rinsing process that causes pattern collapse is replaced with a vapor-phase heating process. By using thermal treatment in a controlled atmosphere instead of liquid rinsing, the harmful surface tension forces are eliminated while maintaining the ability to remove etched material and complete the high aspect ratio pattern etching.
Solution Approach 2:
The process employs an inert or controlled atmosphere during the heating step to prevent unwanted chemical reactions while removing the reaction layer. This inert environment protects the delicate high aspect ratio patterns from damage that would occur with liquid exposure, eliminating pattern collapse while maintaining processing capability.
3Speed
If plasma etching with oxygen is used to etch tantalum nitride, then etching rate is improved, but carbon hard mask is also etched
Solution Approach 1:
The plasma treatment step performs a preliminary reaction with the tantalum nitride surface, forming a reaction layer that contains tantalum-fluorine bonds and nitrogen-hydrogen bonds. This preliminary action prepares the surface for subsequent heating removal while being selective to tantalum nitride, thereby protecting the carbon hard mask from etching while maintaining high etching rate for the target material.
Solution Approach 2:
The process changes parameters by using a plasma composition containing fluorine and hydrogen but no oxygen, and by controlling the plasma power and gas flow rates. These parameter changes enable selective reaction with tantalum nitride to form the reaction layer while preventing carbon hard mask etching, achieving both high etching rate and high selectivity.
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 achieves highly uniform etching across the wafer in-plane direction and pattern depth direction, enhancing processing dimension controllability and improving the yield of semiconductor device manufacturing.
Implementation Method 1
supplying reactive particles containing fluorine and hydrogen but containing no oxygen to a surface of the film layer to form a reaction layer which mainly contains a tantalum-fluorine bond and nitrogen-hydrogen bond
Implementation Method 2
eliminating the reaction layer by heating the film layer
Data Source
AI summary
Provided is an etching technique providing higher uniformity of etching amount and a higher yield of etching processing. An etching method for etching a film layer as a processing object containing nitride of transition metal, the film layer being disposed on a surface of a wafer, includes a step of supplying reactive particles containing fluorine and hydrogen but containing no oxygen to a surface of the film layer to form a reaction layer on the surface of the film layer, and a step of eliminating the reaction layer by heating the film layer.