Plasma Etching Magnetic Film Depth Control
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Solution Overview
Problem
Conventional plasma etching methods for magnetic films using carbon monoxide and ammonia gases face challenges in achieving desired etching depth, especially when the opening size of the mask is narrower than 250 nm, leading to etch stop and reduced etching efficiency.
Innovation Solution
A plasma etching method involving a two-step process using a mixed gas of ammonia and helium, followed by a gas containing oxygen or a hydroxyl group, to achieve the desired etching depth regardless of the mask opening size, with a tantalum film as the mask.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a mixed gas of carbon monoxide and ammonia is used for plasma etching of magnetic film, then etching can be performed on magnetic materials, but etching depth is limited to around 150 nm when mask opening is narrower than 250 nm due to etch stop
Solution Approach 1:
The etching process is divided into multiple sequential steps, each using a different gas mixture tailored to specific etching depth ranges. The first step uses CO-NH3 mixture for initial etching, followed by second and third steps using NH3-O2 or NH3-hydroxyl group gas mixtures to continue etching beyond the 150 nm limit, effectively segmenting the etching journey into manageable phases that overcome the etch stop barrier
Solution Approach 2:
The invention changes the chemical composition parameters of the plasma gas mixture at different etching stages. By transitioning from CO-NH3 gas mixture in the first step to NH3-O2 or NH3-hydroxyl group gas mixtures in subsequent steps, the reactive species and etching chemistry are modified to prevent etch stop and enable continued etching to desired depths of 300 nm or more
2Manufacturing precision
If conventional plasma etching is used on magnetic materials with low volatility, then etching can be performed, but perpendicular shape and desired etching speed cannot be achieved
Solution Approach 1:
The invention modifies the plasma chemistry parameters by using specific gas mixtures (CO-NH3 for first step, NH3-O2 or NH3-hydroxyl group gases for second and third steps) that generate appropriate reactive species for etching low-volatility magnetic materials. These parameter changes enable both perpendicular sidewall formation and acceptable etching speeds by optimizing the balance between physical sputtering and chemical reaction components
3Productivity
If etching time is prolonged to increase shaved quantity, then more material is removed, but etch stop occurs and no further depth increase is achieved
Solution Approach 1:
The etching process employs periodic action by alternating between different gas mixture compositions at different etching stages. The first periodic phase uses CO-NH3 mixture for initial etching, then transitions to NH3-O2 or NH3-hydroxyl group gas mixtures in subsequent periodic phases to remove reaction products and restore etching activity, enabling continued material removal without etch stop even as etching time progresses
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
Enables consistent and controlled etching to a depth of 300 nm or more, even with narrow mask openings, while maintaining a tapered shape and preventing the formation of tantalum oxide that can hinder etching.
Implementation Method 1
a first process to plasma-etch the magnetic film to a desired depth by using a mixed gas of an ammonia gas and a helium gas; and a second process, after the first process, to plasma-etch the magnetic film etched to the desired depth
Implementation Method 2
As a plasma etching method enabling reactive ion etching to such a magnetic material
Implementation Method 3
a dry etching method of using a carbon monoxide (CO) gas to which a nitrogen compound contained gas such as an ammonia (NH3) or amine gas is added as a reaction gas
Implementation Method 4
a second process, after the first process, to plasma-etch the magnetic film etched to the desired depth by using a mixed gas of an ammonia gas and a gas containing the oxygen element or a mixed gas of an ammonia gas and a gas containing a hydroxyl group
Data Source
AI summary
The present invention provides, in a plasma etching method for plasma-etching a magnetic film, a plasma etching method that allows a desired etching depth to be obtained regardless of the opening size of a mask. The present invention is, in a plasma etching method for plasma-etching a magnetic film by using a tantalum film as a mask, characterized by including: a first process to plasma-etch the magnetic film to a desired depth by using a mixed gas of an ammonia gas and a helium gas; and a second process, after the first process, to plasma-etch the magnetic film etched to the prescribed depth by using a mixed gas of an ammonia gas and a gas containing the oxygen element or a mixed gas of an ammonia gas and a gas containing a hydroxyl group.