Amorphous Carbon Sacrificial Layer for DRAM Contact Plug Formation
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Solution Overview
Problem
The miniaturization of DRAMs makes it difficult to form high-reliability contact plugs without short circuits between the contact plug and the bit line, as the etching rate ratio between silicon oxide and silicon nitride films becomes challenging, leading to issues in maintaining sufficient insulation and preventing short circuits.
Innovation Solution
A method involving the use of an amorphous carbon film as a sacrificial interlayer film, which can be dry etched without etching the silicon nitride film, ensuring sufficient thickness remains on the bit line and preventing short circuits, while allowing for conventional techniques to be used in subsequent capacity formation steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the interlayer insulating film is increased to ensure fabrication margin, then the insulation reliability is improved, but the working margin decreases and the formation of capacitance contact plug becomes more difficult
Solution Approach 1:
The patent introduces a silicon nitride film as an intermediary protective layer between the bit line and the capacitance contact plug formation area. This intermediary layer prevents direct contact and potential short circuits while allowing the interlayer insulating film to maintain its necessary thickness for insulation reliability.
Solution Approach 2:
The silicon nitride film is formed on the bit line before the capacitance contact plug is created. This preliminary action establishes a protective barrier in advance, preventing short circuits during subsequent processing steps and eliminating the need to reduce interlayer insulating film thickness.
2Manufacturing precision
If the etching rate ratio between silicon oxide and silicon nitride films is optimized, then the manufacturing precision is improved, but the process control becomes more challenging
Solution Approach 1:
The patent changes the material parameter of the protective film from conventional materials to silicon nitride, which has a significantly different etching rate compared to silicon oxide. This parameter change creates a more favorable etching rate ratio that simplifies process control while improving contact plug formation precision.
Solution Approach 2:
The silicon nitride film is applied locally only where needed - on the bit line structure - rather than uniformly throughout the entire device. This localized application provides precise etching protection where required while maintaining standard processing elsewhere, reducing overall process control 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 prevents short circuits between the contact plug and the bit line by maintaining a sufficient thickness of silicon nitride film, ensuring high-reliability contact plug formation and allowing for conventional capacity formation techniques to be applied.
Implementation Method 1
an amorphous carbon film which covers the whole surface of the bit line; forming a capacitance contact plug which establishes a connection to part of the first contact plug by piercing through the amorphous carbon film and the second interlayer insulating film
Data Source
AI summary
Method of forming a high-reliability contact plug which prevents a short circuit between the plug and a bit line by applying a material having an etching rate ratio of 100 or more with respect to a silicon nitride film which forms a self-aligned contact plug. After the formation of a bit line, whose top surface and side surfaces are covered with a silicon nitride film, a sacrificial interlayer film is formed which covers the whole surface of the bit line, and a contact hole is formed by etching the sacrificial interlayer film and then the lower-layer interlayer insulating film to form a capacitance contact plug. A column of a capacitance contact plug is then formed by removing the sacrificial interlayer film, a third interlayer insulating film is formed on the column, and part of this interlayer is removed to expose a surface of the contact plug.