Hard Mask Patterning via Oxide Pillar Template
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Solution Overview
Problem
High aspect ratio etching in substrate processing, particularly for 3D structures like vertical NAND flash, requires new methods as existing hard mask materials are difficult to pattern using plasma etching due to lack of volatile etch byproducts and low mask selectivity at high ion bombardment energies.
Innovation Solution
A method involving a substrate processing sequence that includes defining a hole pattern in a photoresist/BARC layer, transferring it to a carbon layer, filling with oxide pillars, and then filling the space between these pillars with a hard mask material using physical vapor deposition or chemical vapor deposition, with a tungsten glue layer, followed by planarization and stripping to expose the pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If plasma etching is used to pattern hard mask materials, then etching capability is achieved, but mask selectivity deteriorates and etch resistance is insufficient at high ion bombardment energies
Solution Approach 1:
The patent introduces an intermediary material layer (such as silicon oxide or silicon nitride) between the hard mask material and the underlying layer. This intermediary layer has high etch selectivity compared to the hard mask material, allowing plasma etching to proceed without the hard mask being excessively eroded. The intermediary layer acts as a buffer that protects the hard mask while enabling precise patterning.
Solution Approach 2:
The patent employs composite mask structures combining multiple materials with complementary properties. For example, a stack of different dielectric materials or a combination of organic and inorganic layers is used to achieve both high etch resistance and good pattern definition. The composite structure leverages the strengths of each material to overcome the limitations of single-material masks.
2Reliability
If harder mask materials with high etch resistance are used, then mask durability is improved, but patternability deteriorates due to lack of volatile etch byproducts
Solution Approach 1:
The patent divides the mask function into multiple separate layers, each optimized for specific requirements. One layer provides etch resistance while another layer (such as an organic photoresist or a material with volatile byproducts) enables pattern definition. This segmentation allows each layer to perform its specialized function without compromise.
Solution Approach 2:
The patent changes the physical or chemical parameters of the mask material or processing conditions to enable patterning. For example, using materials that become volatile under specific etching conditions, or adjusting etching parameters (temperature, pressure, gas composition) to enhance the volatility of byproducts from hard mask materials, thereby improving pattern definition.
3Productivity
If high ion energy is used for high aspect ratio etching, then etching speed is improved, but mask selectivity deteriorates
Solution Approach 1:
The patent applies different material properties or protective measures to different regions of the mask structure. For example, the top surface of the mask may have different composition or thickness compared to lower regions, or selective protective coatings are applied to areas requiring higher selectivity. This local differentiation allows high ion energy to be used overall while protecting critical regions.
Solution Approach 2:
The patent performs preliminary actions before the main etching process to prepare the mask and underlying structures. This may include forming protective capping layers, pre-conditioning the mask surface, or creating sacrificial layers that are removed beforehand. These preliminary steps enable the subsequent high-ion-energy etching to proceed with maintained selectivity.
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 method effectively patterns hard mask materials like metal for high aspect ratio features without plasma etching, enhancing etch resistance and selectivity, suitable for 3D scaling applications.
Implementation Method 1
defining a hole pattern in the PR/BARC layer using photolithography
Implementation Method 2
filling the plurality of holes in the hole pattern with oxide to create oxide pillars
Implementation Method 3
filling the plurality of holes in the hole pattern with oxide to create oxide pillars
Implementation Method 4
The glue layer includes a tungsten (W) layer
Data Source
AI summary
A method for processing a substrate includes providing the substrate including a photoresist/bottom anti-reflection coating (PR/BARC) layer, a hard mask layer, a stop layer, a carbon layer and a stack including a plurality of layers. The method includes defining a hole pattern including a plurality of holes in the PR/BARC layer using photolithography; transferring the hole pattern into the carbon layer; filling the plurality of holes in the hole pattern with oxide to create oxide pillars; using a planarization technique to remove the hard mask layer, a remaining portion of the PR/BARC layer and the stop layer; stripping the carbon layer to expose the oxide pillars; filling space between the oxide pillars with hard a mask material including metal; planarizing at least part of the hard mask material; and stripping the oxide pillars to expose the hole pattern in the hard mask material.