Stepped Isolation Insulator for Flash Memory Stress Relief
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Solution Overview
Problem
The scaling down of semiconductor elements in flash memory leads to the use of low-viscosity filling materials that cause stress, resulting in crystal defects in semiconductor regions, which deteriorate the characteristics of the elements formed.
Innovation Solution
The semiconductor memory design incorporates a unique isolation insulator structure with a stepped upper surface, where the first isolation film is set back closer to the semiconductor substrate than the second film, reducing the volume of the insulator and minimizing stress on the active region, thereby reducing crystal defects and improving element characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If element scaling-down is carried out for higher storage density, then storage density is improved, but crystal defects are produced in semiconductor regions due to stress from low-viscosity filling materials
Solution Approach 1:
The patent applies local quality by creating a stepped upper surface structure in the isolation insulator where different regions have different heights. The first isolation film is set back closer to the semiconductor substrate than the second film, creating localized stress relief zones. This local structural variation reduces stress concentration in critical areas while maintaining overall isolation functionality, thereby preventing crystal defects in the semiconductor region.
2Ease of manufacture
If a low-viscosity filling material is used to fill the space between element regions, then ease of manufacture is improved, but stress is produced that creates crystal defects
Solution Approach 1:
The patent changes the geometric parameters of the isolation insulator by creating a stepped upper surface with two different film heights. This parameter modification allows the low-viscosity filling material to be used for ease of manufacture while the stepped structure redistributes the stress field, preventing stress concentration that would cause crystal defects in the semiconductor region.
3Reliability
If the volume of the isolation insulator is reduced by setting back the first film, then stress on the active region is minimized, but device complexity increases
Solution Approach 1:
The isolation insulator is segmented into two distinct films with different heights: a first isolation film set back closer to the semiconductor substrate and a second film extending higher. This segmentation reduces the overall volume of the isolation insulator, minimizing stress on the active region and preventing crystal defects, while the segmented structure itself is achieved through standard semiconductor manufacturing processes.
Data Source
AI summary
According to one embodiment, a semiconductor memory includes a memory cell in a memory cell array which is provided in a semiconductor substrate and which includes a first active region surrounded by a first isolation insulator, a transistor in a transistor region which is provided in the semiconductor substrate and which includes second active regions surrounded by a second isolation insulator. The second isolation insulator includes a first film, and a second film between the first film and the second active region, and the upper surface of the first film is located closer to the bottom of the semiconductor substrate than the upper surface of the second film.