SHB Layer Contact Hole Fabrication for Sub-65nm Precision
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Solution Overview
Problem
Conventional methods for fabricating contact holes in semiconductor wafers face challenges such as optical limitations in photoresist-mask approaches and complexity with metal hard masks, leading to difficulties in achieving desired critical dimensions and profiles, especially for high aspect ratio contact holes beyond 65 nm.
Innovation Solution
A method involving a silicon-containing hard mask bottom anti-reflection coating (SHB) layer, where a thinner photoresist layer is used as a hard mask to etch through the SHB layer, forming a shrunk, tapered opening, and subsequently using the SHB and etching resistive layers as etching hard masks to create a contact hole with improved critical dimension and profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional photoresist-mask approach is used, then the fabrication process is simple, but the optical limitations prevent achieving desired critical dimensions below 65 nm
Solution Approach 1:
The fabrication process is divided into multiple stages: first forming a patterned photoresist layer, then using it to pattern a silicon-containing hard mask layer, and finally using the hard mask to define the contact hole. This segmentation allows each layer to be optimized for its specific function, enabling sub-65 nm precision without requiring the entire process to be simplified
Solution Approach 2:
The invention uses a composite mask structure consisting of a photoresist layer combined with a silicon-containing hard mask layer. The photoresist provides good lithographic properties for pattern formation, while the silicon-containing hard mask provides the necessary etching resistance and dimensional control, together achieving precision beyond what either material could provide alone
2Reliability
If the photoresist thickness is decreased to increase process window and depth of focus, then the photoresist can act as an etching hard mask, but the thickness becomes insufficient for subsequent dry etching
Solution Approach 1:
The mask function is segmented between two layers: the photoresist layer optimized for lithography with sufficient thickness for process window, and the silicon-containing hard mask layer providing the etching resistance. This allows each layer to have the thickness appropriate for its specific function without compromise
Solution Approach 2:
The silicon-containing hard mask layer acts as an intermediary between the photoresist and the underlying dielectric layer. It receives the pattern from the photoresist and transfers it to the dielectric layer during etching, while providing the necessary mechanical support and etching resistance that the thin photoresist cannot provide
3Manufacturing precision
If a metal hard mask is used to increase etching resistance, then the contact process complexity increases due to deposition temperature constraints and remanent metal removal
Solution Approach 1:
The silicon-containing hard mask is designed to be etched away along with the dielectric layer during the contact hole formation process. This disposable approach eliminates the need for separate metal hard mask deposition and removal steps, reducing process complexity while maintaining sufficient etching resistance during the critical pattern transfer step
Solution Approach 2:
The invention changes the material parameter from metal to silicon-containing compound, which fundamentally alters the process requirements. Silicon-containing materials can be deposited at lower temperatures compatible with underlying layers and can be removed by standard wet or vapor HF etching, eliminating the temperature constraints and remanent removal issues associated with metal hard masks
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 enhances the process window and precision in forming contact holes with a larger depth of focus, reducing the complexity of the contact process and achieving the desired after-etch inspection critical dimension and contact hole profile without the need for metal hard masks.
Implementation Method 1
A lithographic process is performed to form a first opening in the photoresist layer
Implementation Method 2
Using the SHB layer and the etching resistive layer as etching hard masks, respectively, etching the etching resistive layer and the dielectric layer
Data Source
AI summary
A method for fabricating a contact hole is provided. A semiconductor substrate having thereon a conductive region is prepared. A dielectric layer is deposited on the semiconductor substrate and the conductive region. An etching resistive layer is coated on the dielectric layer. A silicon-containing hard mask bottom anti-reflection coating (SHB) layer is then coated on the etching resistive layer. A photoresist layer is then coated on the SHB layer. A lithographic process is performed to form a first opening in the photoresist layer. Using the photoresist layer as a hard mask, the SHB layer is etched through the first opening, thereby forming a shrunk, tapered second opening in the SHB layer. Using the etching resistive layer as an etching hard mask, etching the dielectric layer through the second opening to form a contact hole in the dielectric layer.