Boron Nitride Hard Mask Etching for High Aspect Ratio Patterns
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Solution Overview
Problem
The existing methods for manufacturing semiconductor devices face challenges in achieving high aspect ratio etching and sufficient selectivity between photoresist and hard masks, leading to inefficiencies and increased manufacturing costs due to the need for complex multilayered structures like the stacked mask process (SMAP) method.
Innovation Solution
A method involving the formation of a boron nitride (BN) film with high boron concentration as a hard mask, combined with a silicon oxide film, using nanoimprint technology and reactive ion etching with a specific etching gas composition to achieve high selectivity and etch the BN film, thereby simplifying the film structure and reducing the number of stacked layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a photoresist is made thick to enable pattern transfer, then the pattern can be transferred to the hard mask, but the focal depth of lithography does not fit and exposure is disabled
Solution Approach 1:
The patent divides the single thick photoresist layer into multiple thinner photoresist layers stacked together. Each layer has a thickness within the focal depth range of lithography, enabling proper exposure. The combined thickness of multiple layers achieves the required total thickness for pattern transfer capability, thus resolving the contradiction between pattern transfer capability and photoresist thickness.
2Manufacturing precision
If the stacked mask process (SMAP) method is used to transfer pattern to hard mask, then selectivity between photoresist and hard mask is improved, but the number of stacked layers increases and manufacturing cost increases
Solution Approach 1:
The patent combines multiple photoresist layers into a single integrated mask structure that works together to achieve both sufficient thickness and proper lithography exposure. This merged structure eliminates the need for separate intermediate films and multiple etching steps required in the SMAP method, thereby reducing the total number of stacked layers while maintaining high etching selectivity between the photoresist mask and hard mask.
3Manufacturing precision
If reactive ion etching (RIE) using gas containing O2, N2, and H2 is used to etch intermediate film and carbon film, then etching selectivity is increased, but the number of processes increases
Solution Approach 1:
The patent extracts and removes the intermediate film layer from the stacked mask structure, keeping only the essential photoresist layers and hard mask. By eliminating the intermediate film, the need for separate etching processes targeting intermediate films is removed, reducing the total number of etching processes while maintaining high selectivity through optimized RIE gas composition (O2, N2, H2) applied directly to the photoresist-hard mask interface.
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 allows for the formation of high aspect ratio concave portions with improved etching selectivity and reduced manufacturing costs by using a simpler film structure, enabling efficient pattern transfer and miniaturization in semiconductor devices.
Implementation Method 1
etching the first film by using the second film where the pattern is transferred as a mask, with an etching gas that contains fluoromethane (CH3F) and oxygen (O2)
Implementation Method 2
pressing an original plate having a pattern formed in an uneven shape onto the second film to transfer the pattern to the second film
Data Source
AI summary
In one embodiment, a method of manufacturing a semiconductor device includes forming a first film containing boron (B) on a member to be etched, the member being a semiconductor substrate, or a film formed on the semiconductor substrate, and forming a second film formed of a silicon oxide film on the first film. The method further includes pressing an original plate having a pattern formed in an uneven shape onto the second film to transfer the pattern to the second film, and etching the first film by using the second film where the pattern is transferred as a mask, with an etching gas that contains fluoromethane (CH3F) and oxygen (O2) and has an oxygen concentration of 50 to 90 at. %, to transfer the pattern to the first film. The method further includes etching the member by using the first film where the pattern is transferred as a mask, to form a concave portion having the pattern in the member.