Semiconductor Stack Etching With Al2O3 or TiN Hardmask Protection
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Solution Overview
Problem
The challenge in manufacturing high-density three-dimensional semiconductor devices is the limited number of stacked layers due to damage to the top conductor and isolation layers during the deep-hole etching process, which is caused by the low selectivity of carbon-based hardmasks in fluorine-based plasma etching.
Innovation Solution
A method involving the formation of a stack structure with a pair of film layers, where a patterned first hardmask made of aluminum oxide or titanium nitride is used to etch through the stack structure, forming openings that penetrate through the layers without causing significant damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fluorine-based plasma etching is used with carbon-based hardmask, then the etching process can be performed, but the selectivity is low causing damage to top conductor and isolation layers
Solution Approach 1:
The patent introduces an intermediary protective layer between the carbon-based hardmask and the top conductor/isolation layers. This protective layer has high etching selectivity to fluorine-based plasma, allowing the etching process to proceed while protecting the sensitive top layers from damage. The protective layer acts as a buffer that absorbs the harmful etching effects.
Solution Approach 2:
The patent uses a composite mask structure consisting of multiple layers with different material properties. The carbon-based hardmask is combined with a protective layer that has complementary properties - specifically, the protective layer is resistant to fluorine-based plasma etching while the carbon layer provides the necessary patterning capability. This composite approach leverages the strengths of each material.
2Quantity of substance
If the number of stacked layers is increased to improve component density, then the component density increases, but the etching profile becomes non-collimated due to hardmask damage
Solution Approach 1:
The protective layer serves as an intermediary that maintains etching profile collimation even when etching through multiple stacked layers. By preventing hardmask damage, it ensures that the etching front remains uniform and vertical, producing collimated profiles that are essential for high-density stacking.
Solution Approach 2:
The protective layer is applied beforehand to cushion and prevent damage to the hardmask during the etching process. This prior protection ensures that the hardmask maintains its structural integrity and patterning accuracy throughout the etching of multiple stacked layers, enabling higher component density without sacrificing etching precision.
3Ease of manufacture
If deep-hole etching is performed to form through holes in stack structure, then openings can be formed, but the process becomes complex requiring hardmask with low selectivity
Solution Approach 1:
The protective layer simplifies the deep-hole etching process by acting as an intermediary that enables the use of carbon-based hardmasks. Without this protective layer, carbon-based hardmasks would require overly complex multi-layer structures to achieve sufficient protection. The protective layer allows for a simpler, more manufacturable hardmask configuration while still enabling deep-hole etching.
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
The use of aluminum oxide or titanium nitride as the first hardmask improves the etching selectivity and resistance, reducing the damage to the top layers and allowing for a higher number of stacked layers, thus enhancing the component density of three-dimensional semiconductor devices.
Implementation Method 1
fluorine-based plasma etching is used to form through holes
Implementation Method 2
A carbon-based hardmask has a relatively low selectivity for such etching
Data Source
AI summary
A method for manufacturing a semiconductor device includes: forming, on a substrate, a pair of film layers stacked in a vertical direction to form a stack structure, the pair of film layers includes a first material layer and a second material layer sequentially stacked in the vertical direction, the first material layer is an isolation material layer, and the second material layer is a sacrificial material layer or a conductive material layer; forming a patterned first hardmask on a side of the stack structure away from the substrate, the material of the first hardmask including aluminum oxide or titanium nitride; and etching the stack structure by using the patterned first hardmask as a mask to form an opening that penetrates through the stack structure.