Triple Etching Stop Layer for Lithography Mask Substrate Protection
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Solution Overview
Problem
Current negative tone imaging (NTI) technology using a bright mask suffers from significant substrate loss during the developing process, limiting its ability to achieve high image resolution in advanced lithography.
Innovation Solution
A new mask blank structure with a triple etching stop layer comprising sub-layers such as TaN, TaO, and SiON, and a shielding layer, combined with optical proximity correction (OPC) rules, is used to prevent quartz damage during etching, enabling the formation of an island mask with improved critical dimension control and reduced substrate loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If negative tone imaging (NTI) technology using a bright mask is used, then image resolution is improved, but substrate loss occurs during the developing process
Solution Approach 1:
A tri-layer etch stop structure (first etch stop layer, second etch stop layer, and third etch stop layer) is introduced as an intermediary between the mask pattern and the quartz substrate. This etch stop structure prevents direct damage to the substrate during etching while allowing the NTI bright mask to maintain its high resolution imaging capability.
Solution Approach 2:
The etch stop layers are prepared in advance before the actual mask pattern etching. The first etch stop layer and second etch stop layer are formed with specific materials and thicknesses to create a protective barrier that prevents substrate loss during subsequent developing and etching processes.
2Stability of the object's composition
If conventional positive tone imaging (PTI) technology using a dark mask is used, then process stability is maintained, but image resolution cannot be improved further
Solution Approach 1:
The invention changes the imaging mode from positive tone imaging (PTI) to negative tone imaging (NTI), fundamentally altering the photoresist development behavior. This parameter change enables higher resolution imaging while the etch stop structure maintains process stability by preventing substrate damage.
3Device complexity
If a single etch stop layer is used, then manufacturing complexity is reduced, but insufficient protection against quartz damage occurs
Solution Approach 1:
The etch stop function is segmented into three distinct layers with different materials and thicknesses. The first etch stop layer (e.g., TaN, 2-5nm), second etch stop layer (e.g., TaO, 2-3nm), and third etch stop layer (e.g., TaN, 2-5nm) work together to provide comprehensive protection against quartz damage during multiple etching steps.
Solution Approach 2:
The etch stop structure uses composite materials with different chemical and physical properties. The combination of TaN, TaO, and SiON layers creates a multi-functional barrier that provides both etch stopping capability and protection against quartz substrate damage.
Data Source
AI summary
Structure of mask blanks and masks, and methods of making masks are disclosed. The new mask blank and mask comprise a tripe etching stop layer to prevent damages to the quartz substrate when the process goes through etching steps three times. The triple etching stop layer may comprise a first sub-layer of tantalum containing nitrogen (TaN), a second sub-layer of tantalum containing oxygen (TaO), and a third sub-layer of TaN. Alternatively, the triple etching stop layer may comprise a first sub-layer of SiON material, a second sub-layer of TaO material, and a third sub-layer of SiON material. Another alternative may be one layer of low etching rate MoxSiyONz material which can prevent damages to the quartz substrate when the process goes through etching steps three times. The island mask is defined on the mask blank by using various optical proximity correction rules.