PF3 Plasma Etching for MRAM Metal Laminated Films
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Solution Overview
Problem
The existing dry-etching methods for metal thin films in MRAM elements, using chlorine or fluorine gases, result in reaction products with high boiling points that accumulate in the processing chamber, leading to degraded film shapes and difficulty in controlling critical dimensions due to their low vaporization tendency.
Innovation Solution
An etching method utilizing a gas containing PF3 gas to generate plasma for etching and post-etching treatment, which effectively vaporizes and removes reaction products with lower boiling points, ensuring efficient etching and maintaining desired film dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If chlorine gas (Cl2) or fluorine gas (F2) is used for dry-etching metal thin film, then etching capability is improved, but reaction products accumulate in the processing chamber due to high boiling points, degrading film shape and controlling critical dimensions
Solution Approach 1:
The patent changes the chemical composition parameter of the etching gas from conventional chlorine or fluorine gas to a gas containing phosphorus (such as PH3, PF3, or POCl3). This parameter change fundamentally alters the reaction products from high-boiling-point metal chlorides or fluorides to volatile metal phosphides or phosphates, enabling effective vaporization and removal while maintaining etching capability.
Solution Approach 2:
The patent converts the potential harm of reaction product accumulation into a benefit by selecting phosphorus-based etching gases that produce highly volatile reaction products. These products, which would normally be problematic due to their tendency to condense and deposit, are instead designed to vaporize completely at processing temperatures, thereby eliminating the accumulation issue while maintaining effective etching.
2Speed
If chlorine gas (Cl2) or fluorine gas (F2) is used for dry-etching, then etching speed is improved, but reaction products are difficult to remove from the etching surface, making it difficult to control critical dimensions
Solution Approach 1:
The patent changes the chemical parameter of the etching gas to phosphorus-based gases, which fundamentally alters the volatility parameter of the reaction products. The resulting metal phosphides or phosphates have sufficiently high vapor pressures at processing temperatures to be readily removed from the etching surface, thereby enabling precise control of critical dimensions while maintaining high etching speed.
Solution Approach 2:
The patent implements a process where the volatility of reaction products provides inherent feedback control. The highly volatile nature of phosphorus-based reaction products ensures they are rapidly removed from the etching surface, preventing re-deposition and enabling consistent critical dimension control. This self-regulating mechanism maintains etching precision without requiring additional complex control systems.
3Productivity
If high boiling point reaction products are generated during etching, then etching can be performed, but the reaction products remain in the processing chamber and accumulate on wall faces, degrading lower layer film shapes
Solution Approach 1:
The patent changes the chemical composition parameter of the etching gas from chlorine or fluorine-based to phosphorus-based gases. This fundamental parameter change transforms the reaction products from non-volatile metal chlorides or fluorides to volatile metal phosphides or phosphates, enabling them to vaporize and be evacuated from the processing chamber, thereby eliminating accumulation on wall faces and protecting lower layer film shapes.
Solution Approach 2:
The patent converts the potential harm of reaction product deposition into a benefit by using phosphorus-based etching gases. The reaction products, which would normally condense and deposit on chamber walls, are instead designed to remain in the vapor phase at processing temperatures and be efficiently evacuated. This eliminates the harmful accumulation effect while maintaining effective etching of the metal thin film.
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
The use of PF3 gas enables efficient etching and removal of reaction products, improving control over etching processes and preventing accumulation, thus maintaining precise film shapes and dimensions.
Implementation Method 1
generating a plasma by supplying a first gas to a processing chamber and etching the metal laminated film using the generated plasma
Implementation Method 2
etching the metal laminated film using a gas containing PF3 gas
Implementation Method 3
reaction products generated during the etching process have relatively low melting points and boiling points that would enable the reaction products to be vaporized immediately and discharged
Data Source
AI summary
An etching method is provided for etching a multilayer film material that includes a metal laminated film having an insulating layer arranged between a first magnetic layer and a second magnetic layer. The etching method includes an etching step of generating a plasma by supplying a first gas to a processing chamber and etching the metal laminated film using the generated plasma. The first gas is a gas containing PF3 gas.