Reverse Self-Aligned Double Patterning for BEOL Metal Structures

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Solution Overview

Problem

The existing self-aligned double patterning (SADP) process for forming semiconductor devices is complex and costly due to the need for multiple masks or complex cut/block masks to vary the distance between metal structures, which complicates the fabrication process.

Innovation Solution

A reverse SADP process is introduced, where multiple hardmask layers are used, and mandrels are maintained during the formation of sidewall structures, allowing for the variation of metal structure widths and distances without additional masks, by using the mandrels and hardmask layers as etch masks to form trenches for metal structures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If traditional SADP process is used with multiple masks or complex cut/block masks to vary distance between metal structures, then manufacturing precision is improved, but device complexity and manufacturing cost increase

Engineering Contradiction:

Improvedistance control between metal structuresVSAvoidfabrication process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent inverts the traditional SADP sequence by first forming the sidewall structures on the mandrels, then removing the mandrels, and finally forming the metal structures in the exposed spaces. This reverse approach eliminates the need for complex cut/block masks while maintaining precise distance control, as the mandrel width directly determines the spacing between metal structures without requiring additional patterning steps

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent extracts the mandrel removal step to occur after sidewall formation but before metal structure deposition. By removing the mandrel at this intermediate stage, the spaces between sidewalls are exposed and can be directly filled with metal structures, eliminating the need for complex masking operations that would otherwise be required to define these spaces

Inventive Principle:

Principle #2Taking out (Extraction)

2Manufacturing precision

If multiple masks are used to vary metal structure widths and distances, then manufacturing precision is improved, but productivity decreases due to additional process steps

Engineering Contradiction:

Improvemetal structure dimensions and spacingVSAvoidfabrication throughput

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

By inverting the process sequence to form sidewalls before removing mandrels and before forming metal structures, the patent consolidates multiple patterning operations into a single mandrel-based definition step. This reduces the number of sequential mask steps required, thereby increasing fabrication throughput while maintaining precise dimensional control through the mandrel geometry

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent performs preliminary action by forming the sidewall structures on the mandrels before removing the mandrels. This preliminary sidewall formation establishes the precise spacing framework in advance, allowing subsequent metal structure formation to proceed more rapidly without requiring additional complex masking steps

Inventive Principle:

Principle #10Preliminary action

3Manufacturing precision

If complex cut/block masks are used to control metal structure spacing, then manufacturing precision is improved, but ease of manufacture deteriorates

Engineering Contradiction:

Improvedistance between metal structuresVSAvoidfabrication simplicity

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent simplifies manufacturing by inverting the traditional approach: instead of using complex cut/block masks to define spaces between metal structures, it forms sidewalls on simple mandrels, removes the mandrels, and directly fills the exposed spaces with metal. This eliminates the need for complex masking while maintaining precise spacing control through the mandrel width

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent uses the mandrel as a template or copy that defines the spacing pattern. By forming sidewalls on the mandrel and then removing the mandrel, the spacing pattern is copied into the final metal structure arrangement without requiring complex masks, thereby simplifying the fabrication process while maintaining precision

Inventive Principle:

Principle #26Copying

Data Source

PatentUS9564361B2Reverse self aligned double patterning process for back end of line fabrication of a semiconductor device

Publication Date: 2017.02.07 QUALCOMM INC

AI summary

In a particular embodiment, a method includes forming a second hardmask layer adjacent to a first sidewall structure and adjacent to a mandrel of a semiconductor device. A top portion of the mandrel is exposed prior to formation of the second hardmask layer. The method further includes removing the first sidewall structure to expose a first portion of a first hardmask layer. The method also includes etching the first portion of the first hardmask layer to expose a second portion of a dielectric material. The method also includes etching the second portion of the dielectric material to form a first trench. The method also includes forming a first metal structure within the first trench.