Phase Change Alloy Etch Using Bromine Plasma
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Solution Overview
Problem
Existing etching processes for phase change memory devices, particularly those using GST alloys, face challenges in achieving precise control over the etching of phase change layers and second electrode layers without damaging the GST material, leading to suboptimal resistance structures and performance.
Innovation Solution
A method and apparatus utilizing a plasma processing chamber with a bromine-containing etch gas to etch the phase change and second electrode layers, maintaining low temperatures and specific gas flow ratios to minimize damage and achieve vertical sidewalls, thereby preserving the GST material's integrity and resistance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching processes are used on phase change layers, then etching can proceed, but the GST material becomes damaged and corroded, leading to suboptimal resistance structures
Solution Approach 1:
The patent changes the chemical parameters of the etching process by using a bromine-containing compound (such as HBr) as the etch gas instead of conventional etchants. This parameter change enables precise etching of the phase change layer while minimizing damage to the GST material, as bromine-based etching provides selective removal of oxidized GST without excessive corrosion.
Solution Approach 2:
The patent employs an oxidizing environment during etching by introducing oxygen or using oxygen-containing compounds in the plasma process. The GST layer is first oxidized to form GSTOx, which is then selectively etched by the bromine-containing compound. This two-step mechanism (oxidation followed by selective etching) allows precise control over the etching process while protecting the underlying GST material from damage.
2Manufacturing precision
If etching is performed to remove oxidized GST, then the phase change layer can be patterned, but excessive corrosion occurs, degrading device performance
Solution Approach 1:
The patent applies partial action by controlling the etching process to remove only the oxidized portion of the GST layer (GSTOx) while leaving the bulk GST material intact. The bromine-containing etch gas is used in controlled amounts and for controlled durations, enabling selective removal of the oxidized surface layer without excessive corrosion of the underlying crystalline or amorphous GST regions. This partial etching approach maintains pattern definition while minimizing material loss.
3Reliability
If high selectivity etching is used to protect GST material, then material integrity is maintained, but etching speed and productivity may be reduced
Solution Approach 1:
The patent applies preliminary action by performing oxidation of the GST layer before the actual etching step. The GST layer is first exposed to oxygen plasma or oxygen-containing gas to form a thin oxidized layer (GSTOx) on the surface. This preliminary oxidation step creates a chemically distinct layer that is highly selective to the subsequent bromine-based etching process. The oxidation prepares the surface for selective removal while protecting the bulk GST material, thereby maintaining both high selectivity and acceptable etching rates.
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 solution enables precise etching of phase change memory devices with minimal corrosion and high etch selectivity, resulting in improved resistance structures and device performance by maintaining the GST material's crystalline and amorphous resistance states effectively.
Implementation Method 1
forming a plasma from the etch gas
Data Source
AI summary
A method of forming devices is provided. A phase change layer is provided. The phase change layer is etched by providing an etch gas comprising a bromine containing compound and forming a plasma from the etch gas. The phase change layer is of a material that may be heated by a current and then when cooled, either forms an amorphous material or a crystalline material, depending on how fast the material is cooled. In addition, the amorphous material has a resistance at least several times greater than the crystalline material.