Neckless Polymeric Hard Mask for Dielectric Etching
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Solution Overview
Problem
Conventional semiconductor processing methods face challenges in achieving high-resolution, deep etching of dielectric layers due to the formation of necks in polymeric hard masks, which distort the etched feature profiles, especially for high aspect ratio contact (HARC) features.
Innovation Solution
The method involves etching neckless mask features into a polymeric hard mask using a plasma processing chamber, followed by a treatment gas to selectively remove the necks, and then using a different plasma etch gas to etch the dielectric layer, ensuring improved feature profiles without necking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional plasma etching is used to etch deep features in dielectric layers, then etching depth can be achieved, but neck formation occurs in the mask features causing profile distortion
Solution Approach 1:
The patent applies parameter changes by switching between different plasma chemistry regimes during the etching process. A first plasma chemistry (e.g., CF4-based) is used for initial etching, then parameters are changed to a second plasma chemistry (e.g., C4F8-based) to fill and smooth the neck region, and finally parameters are changed again to complete the deep etch with proper profile control
Solution Approach 2:
The patent uses preliminary action by first etching the mask features with a controlled chemistry that prevents excessive necking, then performing a preliminary fill step to deposit material in the neck region before completing the final etch. This preliminary preparation ensures the mask maintains its profile throughout the deep etching process
2Device complexity
If photoresist material is used directly for masking during deep etching, then process simplicity is maintained, but mask erosion and profile distortion occur
Solution Approach 1:
The patent employs composite materials by combining photoresist with a hard mask layer (such as silicon oxide or silicon nitride) to create a composite masking structure. The photoresist provides pattern definition while the hard mask provides erosion resistance, together maintaining profile integrity during deep etching without significantly increasing process complexity
3Productivity
If single-step plasma etching is used for dielectric layer removal, then productivity is maintained, but feature profile control deteriorates
Solution Approach 1:
The patent segments the single etching step into multiple sequential plasma chemistry steps, each optimized for a specific function: initial etching, neck filling/profile correction, and final deep etching. This segmentation enables precise profile control at each stage while maintaining overall productivity through efficient process integration
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 results in enhanced etched profiles with reduced tapering, particularly beneficial for high aspect ratio contact features, by eliminating necks in the mask features, thereby improving the critical dimensions and aspect ratios of the etched features.
Implementation Method 1
generating a plasma from the mask etchant gas
Implementation Method 2
generating a plasma from the treatment gas
Implementation Method 3
generating a plasma from the dielectric layer etch gas
Data Source
AI summary
A method for etching features into a dielectric layer over a substrate and existent below a polymeric hard mask is provided. The substrate is placed in a plasma processing chamber. Mask features are etched into the polymeric hard mask and necks are formed inadvertently. A plasma treatment process performed before the dielectric etch step process can selectively etch away the necks. As a result, neckless features are created into the polymeric hardmask. Features etched into the underneath dielectric layer through the neckless polymeric hard mask have straight profiles.