MRAM Source Line and Contact Plug Formation via Triple Patterning
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Solution Overview
Problem
The challenge in manufacturing magnetoresistive random access memory (MRAM) devices is the difficulty in forming fine patterns and preventing failures due to contact between source lines and contact plugs, which is exacerbated by the decreasing design rule and the need for precise and minute feature sizes.
Innovation Solution
A method involving triple patterning technology (TPT) is used to form fine patterns on a substrate, where wet etching processes create openings for source lines and contact plugs, ensuring they do not overlap and reducing the risk of short circuits by using conductive materials and capping layers, and dry etching processes are employed to protect the source lines during pattern removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If design rule is decreased to form finer patterns, then manufacturing precision is improved, but the risk of contact between source lines and contact plugs increases causing short circuits
Solution Approach 1:
The patent applies triple patterning technology to divide the pattern formation process into three separate lithography and etching steps. This segmentation allows for precise control of fine patterns while maintaining adequate spacing between source lines and contact plugs, thus preventing short circuits even at reduced design rules.
Solution Approach 2:
The patent performs preliminary actions by forming sacrificial patterns and spacers before final pattern definition. These preliminary structures guide the subsequent etching processes to ensure proper spacing and prevent contact between conductive elements, addressing the short circuit risk before it occurs.
2Ease of manufacture
If wet etching is used to form openings, then manufacturing ease is improved, but selectivity control becomes more difficult affecting pattern precision
Solution Approach 1:
The patent introduces sacrificial patterns and spacer structures as intermediary elements that mediate between the wet etching process and the final pattern. These intermediaries provide physical guides that ensure precise pattern formation while allowing the use of simple wet etching chemistry, thus maintaining both ease of manufacture and pattern accuracy.
Solution Approach 2:
The patent changes the physical parameters of the etching process by using spacer thickness and sacrificial pattern dimensions as control variables. By adjusting these parameters, the process achieves high precision pattern definition while maintaining the simplicity of wet etching, resolving the contradiction between ease of manufacture and pattern accuracy.
3Manufacturing precision
If dry etching is used to remove second patterns, then manufacturing precision is improved, but source line protection becomes more complex
Solution Approach 1:
The patent employs spacer structures that automatically protect source lines during the dry etching process. The spacers serve as self-forming masks that eliminate the need for additional protective layers or complex process sequencing, thus achieving high precision pattern definition without significantly increasing device complexity.
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 allows for the successful formation of minute-sized source lines and contact plugs without failures, enhancing the manufacturing of MRAM devices by preventing short circuits and ensuring reliable electrical connections.
Implementation Method 1
Some of the second patterns are removed to form first openings each of which extends in the first direction... a wet etching process may be used to form both the first openings and the fourth openings
Implementation Method 2
Portions of the second patterns that are exposed by the second openings are removed to form third openings... the portions of the second patterns exposed by the second openings may be removed by a dry etching process
Data Source
AI summary
In a method of an MRAM device, first and second patterns are formed on a substrate alternately and repeatedly in a second direction. Each first pattern and each second pattern extend in a first direction perpendicular to the second direction. Some of the second patterns are removed to form first openings extending in the first direction. Source lines filling the first openings are formed. A mask is formed on the first and second patterns and the source lines. The mask includes second openings in the first direction, each of which extends in the second direction. Portions of the second patterns exposed by the second openings are removed to form third openings. Third patterns filling the third openings are formed. The second patterns surrounded by the first and third patterns are removed to form fourth openings. Contact plugs filling the fourth openings are formed.