Semiconductor Contact Structure With Vertical Sidewalls and Overlay Margin

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Solution Overview

Problem

The scaling down of semiconductor devices poses challenges in achieving improved quality, yield, performance, and reliability while reducing complexity, particularly in forming contact structures with vertical sidewalls and maintaining a large overlay window to the bottom conductive layer.

Innovation Solution

A semiconductor device fabrication method using a photomask with a translucent layer and an opaque layer, where the photomask is used to pattern a stack structure, forming a contact structure with a body portion and a contact portion. The body portion has a greater width than the contact portion, allowing for vertical contact sidewalls and a large overlay window to the bottom conductive layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional photomask patterning is used, then manufacturing process is simple, but contact structure cannot achieve both vertical sidewalls and large overlay window

Engineering Contradiction:

Improvecontact structure geometryVSAvoidphotomask structure

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The photomask is segmented into three distinct layers: a first opaque layer for defining the contact opening, a translucent layer for partial exposure control, and a second opaque layer for defining the body portion. This segmentation allows each layer to contribute differently to the final pattern, enabling vertical sidewalls while maintaining a large overlay window without requiring complex single-layer photomasks

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the photomask are assigned different optical properties (opaque vs. translucent) to achieve different patterning effects in different areas. The translucent layer provides partial exposure that creates the desired sidewall profile in the contact opening region, while the opaque layers provide complete blocking where full patterning is needed for the body portion

Inventive Principle:

Principle #3Local quality

2Productivity

If contact structure width is reduced to improve density, then overlay window decreases, but contact resistance increases

Engineering Contradiction:

Improvedevice densityVSAvoidcontact resistance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The contact structure is designed with asymmetric dimensions: the contact opening has a smaller width (first width) for high density, while the body portion has a larger width (second width greater than first width) for low contact resistance. This asymmetric design allows the structure to optimize both density and electrical performance simultaneously

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent transitions from a single-dimensional width parameter to a two-dimensional width profile by creating a contact structure where the body portion width differs from the contact opening width. This dimensional change allows optimization of both density (narrow contact opening) and contact resistance (wide body portion) in the same structure

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Manufacturing precision

If etching process is aggressive to form narrow contacts, then under-etching risk increases, but manufacturing precision improves

Engineering Contradiction:

Improvecontact opening dimensionsVSAvoidunder-etching defect

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The photomask is designed with the body portion pattern formed in advance using the second opaque layer, creating a wider protective structure before the actual contact opening etch. This preliminary formation of the wider body portion provides a protective overhang that prevents under-etching defects while allowing precise contact opening dimensions to be achieved

Inventive Principle:

Principle #10Preliminary action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The method improves contact resistance and reduces the risk of under-etching, leading to enhanced yield and performance of the semiconductor device.

Implementation Method 1

patterning the pre-process mask layer using the photomask to form a patterned mask layer including a mask region corresponding to the opaque layer, a region of body portion corresponding to the translucent layer

Methodology Applied

Scientific EffectPhotolithography: Photopolymerisation

Data Source

PatentUS12283518B2Method for fabricating semiconductor device with contact structure

Publication Date: 2025.04.22 NAN YA TECH

AI summary

The present disclosure provides a method for fabricating a semiconductor device including providing a photomask including an opaque layer on a mask substrate and surrounding a translucent layer on the mask substrate, wherein the translucent layer includes a mask opening of contact portion which exposes a portion of the mask substrate; providing a stack structure including an etch stop layer on a bottom conductive layer and a first inter-dielectric layer on the etch stop layer, and forming a pre-process mask layer on the stack structure; patterning the pre-process mask layer using the photomask to form a patterned mask layer including a mask region corresponding to the opaque layer, a region of body portion corresponding to the translucent layer, and a hole of contact portion corresponding to the mask opening of contact portion.