NAND Flash Electrode Trench Thickness for Barrier Metal Continuity
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Solution Overview
Problem
In NAND flash memory devices with a floating gate structure, the presence of steps between electrode films can cause the barrier metal film to thin or disconnect, leading to unwanted failures due to direct contact with the underlying silicon film, especially when the upper electrode film is thin.
Innovation Solution
A nonvolatile semiconductor storage device design where a third electrode film fills a trench with a thickness equal to or less than half the width of the trench, ensuring a planar surface for the barrier metal film and preventing disconnection, and a manufacturing process that includes etching and planarization to maintain even thickness and prevent steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a thin upper electrode film is used, then the device structure is simplified and manufacturing is easier, but steps are formed between electrode films causing barrier metal film disconnection
Solution Approach 1:
The patent changes the thickness parameter of the third electrode film to be equal to or less than half the trench width, which fundamentally alters the geometric relationship between the electrode film and trench. This parameter change eliminates step formation while maintaining electrical connectivity, resolving the contradiction between simplified structure and barrier metal film continuity.
2Manufacturing precision
If the upper electrode film thickness is reduced, then manufacturing precision requirements are relaxed, but steps occur leading to barrier metal film thinning or disconnection
Solution Approach 1:
By establishing a specific parameter relationship (third electrode film thickness ≤ 1/2 trench width), the patent transforms the manufacturing precision requirement from controlling absolute thickness to controlling the relative proportion between thickness and trench width. This resolves the contradiction by making the structure inherently step-free regardless of absolute film thickness variations.
3Reliability
If a thick upper electrode film is used, then steps are suppressed and barrier metal film continuity is maintained, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent identifies the optimal parameter range where the third electrode film thickness is equal to or less than half the trench width. This parameter optimization achieves barrier metal film continuity without requiring excessive film thickness, thus maintaining device simplicity while ensuring reliability.
Data Source
AI summary
A nonvolatile semiconductor storage device includes a semiconductor substrate; a first insulating film disposed above the semiconductor substrate; a first electrode film disposed above the first insulating film; a second insulating film disposed above the first electrode film; a second electrode film disposed above the second insulating film; a third electrode film filling a first trench and overlying the second electrode film, the first trench having a first width and a first depth and extending through the second electrode film and the second insulating film and into the first electrode film; and a first barrier metal film and a first metal film disposed above the third electrode film; wherein the third electrode film above the second electrode film has a first thickness equal to or less than ½ of the first width of the first trench.