U-Shaped Insulating Film for Flash Memory Contact Plug Protection
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Solution Overview
Problem
In flash memory devices, the miniaturization of memory cells leads to narrower bit lines, making it difficult to form small contact plugs without short-circuiting the semiconductor substrate, causing malfunction due to positional displacement of contact holes.
Innovation Solution
The semiconductor device incorporates a second insulating film with a U-shaped cross-sectional shape, composed of a different material than the first insulating film, which is formed to extend over the bit line and adjoin its side surface, preventing the contact plug from contacting the semiconductor substrate even when the contact hole is displaced by being harder to etch than the first insulating film and interlayer insulating film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the memory cell is miniaturized to increase integration density, then the bit line width is reduced, but the contact plug formation becomes difficult due to high risk of short-circuiting the semiconductor substrate
Solution Approach 1:
The patent applies preliminary action by forming the second insulating film (U-shaped insulating film) before forming the contact hole. This U-shaped insulating film extends in the first direction beyond the bit line width, creating a pre-established protective structure that prevents contact plug misalignment from causing substrate short-circuits. The protective structure is prepared in advance, allowing the contact hole to be formed with relaxed precision requirements.
Solution Approach 2:
The patent implements beforehand cushioning by creating the U-shaped insulating film that extends beyond the bit line width in the first direction. This extended insulating film acts as a cushion or buffer zone that absorbs the impact of contact hole positional displacement, preventing the contact plug from directly short-circuiting the semiconductor substrate even when the contact hole is misaligned.
2Manufacturing precision
If the contact hole size is reduced to match the narrower bit line, then the electrical coupling is improved, but the positional displacement risk increases causing substrate contact
Solution Approach 1:
The patent applies segmentation by dividing the insulating film structure into multiple functional parts: the first insulating film covering the bit line, and the second U-shaped insulating film extending beyond the bit line width. This segmented structure allows the contact hole to be precisely aligned with the bit line for good electrical coupling, while the extended second insulating film provides a separate protective function against substrate short-circuits.
Solution Approach 2:
The patent uses the second U-shaped insulating film as an intermediary protective layer between the contact plug and the semiconductor substrate. This intermediary structure mediates the interaction between the contact plug and substrate, preventing direct contact even when the contact hole is displaced, thus eliminating the trade-off between alignment precision and short-circuit prevention.
3Device complexity
If a single-layer insulating film is used, then the device structure is simplified, but the contact plug cannot be protected from substrate contact when contact hole is displaced
Solution Approach 1:
The patent applies local quality by making the second insulating film have different properties than the first insulating film. Specifically, the second insulating film has a different material composition and extends beyond the bit line width in the first direction, providing localized protection where it is most needed (at the edges where substrate short-circuits are most likely to occur) while maintaining simplicity elsewhere.
Solution Approach 2:
The patent uses composite materials by combining different insulating film materials with different properties. The first insulating film and second insulating film have different material compositions, allowing each to perform its specific function optimally. This composite structure provides both the electrical insulation needed for normal operation and the extended protection against substrate short-circuits, achieving reliable contact plug protection without excessive complexity.
Data Source
AI summary
A semiconductor device and a method for manufacturing the semiconductor device is disclosed. The semiconductor device includes a bit line formed to extend into a semiconductor substrate, a charge storage layer formed on the semiconductor substrate, a word line formed above the charge storage layer to extend across the bit line, a gate electrode formed on the charge storage layer under the word line and between bit lines, a first insulating film formed over the bit line and to extend in the direction of the bit line and a second insulating film that includes a different material than that of the first insulating film and formed to adjoin a side surface of the first insulating film. In addition, the semiconductor device includes an interlayer insulating film that includes a different material from that of the second insulating film that is formed on the first insulating film and the second insulating film and a contact plug coupled to the bit line and formed to penetrate through the first insulating film and the interlayer insulating film and to be sandwiched by the second insulating film.