Dual-Tier Misalignment Mark for 3D Memory Pillar Alignment

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Solution Overview

Problem

Despite misalignment inspection using misalignment marks, misalignment between pillars and upper-layer wiring in three-dimensional nonvolatile memory devices can still occur due to inclined formation of pillars and marks, leading to inaccurate detection and potential defects in the manufacturing process.

Innovation Solution

The semiconductor memory device employs a dual-tier misalignment mark system, including marks for optical and electron microscope inspection, with dummy pillars and plugs to accurately assess misalignment between pillars and holes, allowing for precise detection and quantification of misalignment using both optical and electron microscopy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If misalignment inspection is performed using conventional misalignment marks, then inspection capability is provided, but accurate detection of misalignment cannot be ensured due to inclined formation of pillars and marks

Engineering Contradiction:

Improvemisalignment detection accuracyVSAvoiddetection reliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The misalignment mark is divided into multiple segments: a first mark formed in the first tier, a second mark formed in the second tier, and a third mark formed in the first tier. This segmentation allows for comprehensive misalignment detection from multiple reference points, improving both measurement precision and reliability by compensating for inclined formation issues.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a third mark as an intermediary reference element formed in the first tier. This third mark serves as a mediator for comparison between the first and second marks, enabling accurate misalignment detection even when pillars or marks are inclined, thereby resolving the contradiction between measurement precision and detection reliability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If misalignment marks are formed in the same process as pillars, then manufacturing complexity is reduced, but accurate misalignment inspection cannot be performed due to inclined formation

Engineering Contradiction:

Improvemanufacturing process complexityVSAvoidmisalignment mark alignment precision

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The misalignment mark system is segmented into multiple marks formed at different tiers (first tier and second tier). This segmentation allows the marks to be formed in the same manufacturing process as pillars while maintaining alignment precision, as each mark serves as a reference for its respective tier.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent extends the misalignment mark structure into the vertical dimension by forming marks in both the first tier and second tier. This dimensional extension enables accurate misalignment inspection without increasing horizontal manufacturing complexity, as the additional mark is formed during the same vertical stacking process.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Device complexity

If single-tier misalignment marks are used, then device structure is simplified, but accurate misalignment detection between multiple tiers cannot be achieved

Engineering Contradiction:

Improvemisalignment mark structure complexityVSAvoidinter-tier misalignment detection precision

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The misalignment mark is segmented across multiple tiers, with the first mark in the first tier, the second mark in the second tier, and the third mark in the first tier. This segmentation enables accurate inter-tier misalignment detection while keeping each individual mark structure simple, resolving the contradiction between structural simplicity and measurement precision.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The multi-tier misalignment mark system serves multiple functions: detecting misalignment within the first tier, detecting misalignment within the second tier, and detecting misalignment between tiers. This multi-functionality achieves accurate inter-tier detection without proportionally increasing structural complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS11276707B2Semiconductor memory device and method for manufacturing semiconductor memory device

Publication Date: 2022.03.15 KIOXIA CORP

AI summary

According to one embodiment, a semiconductor memory device includes a stacked body disposed in a first tier, the stacked body including a plurality of conductive layers stacked via an insulating layer; a first pillar that extends in the stacked body in a stacking direction of the stacked body; a first upper structure disposed in a second tier upper than the first tier; and a misalignment mark for inspecting misalignment between the first tier and the second tier, wherein the misalignment mark includes a second pillar that extends the first tier of the misalignment inspection region in the stacking direction, and a second upper structure disposed in the second tier of the misalignment inspection region and superposed on the second pillar in a top view.