Mask Layer Density Control for Etching Verticality
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Solution Overview
Problem
Conventional etching methods for NAND-type flash memory devices with three-dimensional structures result in varying widths of openings, leading to differences in the etching target layer, which affects the verticality and uniformity of the etched features.
Innovation Solution
An etching method involving a two-step process where a plasma reaction product is deposited on a mask layer with a coarse and dense region, followed by etching, using specific gas mixtures to control the width of openings by varying the plasma reaction product deposition and etching conditions, including the use of silicon-containing, oxygen-containing, and hydrogen-containing gases to adjust the width uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a plasma reaction product is deposited on the mask layer to protect the wall surface and enhance verticality, then the verticality of the wall surface is improved, but the width of openings varies across different regions due to differences in plasma reaction product deposition
Solution Approach 1:
The mask layer is designed with spatially varying properties: a dense region surrounding each opening and a coarse region in the center. This local quality difference causes controlled variations in plasma reaction product deposition, where the dense region receives more deposition than the coarse region, thereby compensating for width variations and achieving uniform opening widths across different locations
Solution Approach 2:
The mask layer is prepared in advance with predetermined density variations (dense and coarse regions) before the etching process. This preliminary structuring ensures that when plasma reaction products are deposited during etching, the distribution is controlled to maintain uniform opening widths, preventing width variations before they occur
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 method effectively reduces the differences in opening widths across the etching target layer, improving the verticality and uniformity of the etched features by controlling the plasma reaction product distribution and etching rates, thereby enhancing the manufacturing process for NAND-type flash memory devices.
Implementation Method 1
depositing a plasma reaction product on a mask layer made of an organic film formed on the etching target layer
Implementation Method 2
etching the etching target layer... in the method in which a plurality of openings such as deep holes is formed in an etching target layer... the etching of the multilayer film is performed
Data Source
AI summary
Disclosed is an etching method for etching an etching target layer. The etching method includes: a first step of depositing a plasma reaction product on a mask layer made of an organic film formed on the etching target layer; and after the first step, a second step of etching the etching target layer. The mask layer includes a coarse region in which a plurality of openings are formed, and a dense region surrounding the coarse region. The mask layer exists more densely in the dense region than in the coarse region. The coarse region includes a first region and a second region positioned close to the dense region compared to the first region. In the second step of the etching method, a width of the openings in the first region becomes narrower than a width of the openings in the second region.