Top Electrode Bump for MRAM Pillar Shadowing and Gap-Fill
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Solution Overview
Problem
Conventional methods for forming dense arrays of pillar-type memory devices face challenges such as shadowing during ion beam etching, leading to dirty pillar sidewalls and increased yield loss, as well as issues with interlayer dielectric fill between tightly packed pillars, which can result in electrical shorts.
Innovation Solution
The approach involves forming pillar-type memory devices with a thinner top electrode and a semi-spherical conductive bump on top, which increases the effective height of the top electrode, reducing shadowing and improving interlayer dielectric fill by using a self-leveling dielectric material and a second encapsulation material to create a v-shaped gap between pillars, facilitating better contact formation and reducing electrical shorts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional thick top electrode is used in pillar-type memory devices, then the electrode provides sufficient structural support and electrical connectivity, but it causes shadowing during ion beam etching leading to dirty pillar sidewalls and increased yield loss
Solution Approach 1:
The top electrode is segmented into two distinct parts: a thin base layer that minimizes shadowing during ion beam etching, and a separate semi-spherical conductive bump that provides the necessary electrical connectivity and structural support. This segmentation allows each part to optimize its function without the compromises required by a single thick electrode structure.
Solution Approach 2:
The electrode structure transitions from a conventional planar thin film to a three-dimensional semi-spherical bump configuration. This dimensional change allows the electrode to maintain adequate height and connectivity function while the base layer remains thin enough to avoid shadowing issues during etching processes.
2Productivity
If pillar-type memory devices are tightly packed to increase density, then the number of devices per chip increases, but interlayer dielectric fill becomes problematic leading to electrical shorts
Solution Approach 1:
The semi-spherical shape of the conductive bump creates a curved top surface that facilitates better interlayer dielectric material flow and complete gap-fill between adjacent pillars. The spherical geometry eliminates sharp corners and flat surfaces that could trap air pockets or prevent proper dielectric conformal coverage, thereby preventing electrical shorts while maintaining high device density.
3Object-generated harmful factors
If the top electrode is made thinner to reduce shadowing, then shadowing during ion beam etching is reduced, but the electrode height is insufficient for proper contact formation
Solution Approach 1:
The electrode function is divided between two components: the thin base layer minimizes shadowing during etching, while the added semi-spherical bump provides the necessary height for contact formation. This segmentation allows optimization of each function independently without compromise.
Solution Approach 2:
The semi-spherical conductive bump acts as an intermediary structure that bridges the thin base electrode layer and the overlying contact structures. It provides the necessary mechanical support and electrical connectivity height while the thin base layer maintains the low-shadowing characteristic.
Data Source
AI summary
An approach to provide a pillar-type memory device with a bump of a conductive material on a top electrode of the pillar-type memory device. The top electrode is composed of a thin layer of the top electrode material. The bump of the conductive material increases the height of the top electrode after pillar formation for the pillar-type memory device. The pillar-type memory device includes the bump of the conductive material with a semi-sphere-like bump of the conductive metal that is slightly wider than the top electrode of the pillar-type memory device. A contact connects with the bump of the conductive material on the top electrode.