Dual Sacrificial Layer Mask for High Aspect Ratio Patterning

Solution Overview

Problem

As microelectronic devices become more integrated, the high aspect ratio of photoresist patterns leads to collapse, and reducing photoresist thickness to prevent collapse results in poor masking performance, even with the use of hard masks.

Innovation Solution

A method involving the use of two sacrificial layers, with one layer being an amorphous carbon layer and the other a spin-on hard mask, to form a mask structure that allows for the creation of fine patterns in the lower layer by patterning trenches and openings, enabling the formation of high aspect ratio features without collapsing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If photoresist thickness is increased to maintain masking performance, then masking performance is improved, but photoresist pattern collapse occurs due to high aspect ratio

Engineering Contradiction:

Improvemasking performanceVSAvoidphotoresist pattern stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The mask structure is segmented into multiple layers: a lower sacrificial layer (amorphous carbon) and an upper sacrificial layer (spin-on hard mask), with the photoresist pattern formed on top. This segmentation allows each layer to perform its specific function - the lower sacrificial layer provides structural support to prevent collapse, while the upper sacrificial layer maintains masking performance, resolving the contradiction between thickness and stability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The lower sacrificial layer acts as an intermediary between the substrate and the photoresist pattern. It provides mechanical support to the photoresist pattern during the patterning process, preventing collapse due to high aspect ratio, while being removable afterward. This intermediary structure enables the use of thinner photoresist without sacrificing stability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Stability of the object's composition

If photoresist thickness is decreased to prevent collapse, then photoresist pattern stability is improved, but masking performance deteriorates

Engineering Contradiction:

Improvephotoresist pattern stabilityVSAvoidmasking performance

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The mask structure is segmented into multiple layers: a lower sacrificial layer (amorphous carbon) and an upper sacrificial layer (spin-on hard mask), with the photoresist pattern formed on top. This segmentation allows each layer to perform its specific function - the lower sacrificial layer provides structural support to prevent collapse, while the upper sacrificial layer maintains masking performance, resolving the contradiction between thickness and stability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The mask structure uses composite materials - amorphous carbon for the lower sacrificial layer and spin-on hard mask material for the upper sacrificial layer. Each material is selected for its specific properties: amorphous carbon provides mechanical strength and support, while the spin-on hard mask provides good masking performance. This composite approach allows thin photoresist patterns to be stable while maintaining effective masking.

Inventive Principle:

Principle #40Composite materials

3Reliability

If hard mask is used to improve masking performance, then masking performance is improved, but photoresist pattern collapse still occurs

Engineering Contradiction:

Improvemasking performanceVSAvoidphotoresist pattern stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The mask structure is segmented into multiple layers: a lower sacrificial layer (amorphous carbon) and an upper sacrificial layer (spin-on hard mask), with the photoresist pattern formed on top. This segmentation allows each layer to perform its specific function - the lower sacrificial layer provides structural support to prevent collapse, while the upper sacrificial layer maintains masking performance, resolving the contradiction between thickness and stability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of relying solely on increasing photoresist thickness in the vertical dimension, the solution adds another dimension by introducing a lower sacrificial layer beneath the photoresist pattern. This lower layer provides the necessary mechanical support without requiring the photoresist itself to be thick, thus preventing collapse while maintaining the photoresist's masking function.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS9012326B2Methods for patterning microelectronic devices using two sacrificial layers

Publication Date: 2015.04.21 SAMSUNG ELECTRONICS CO LTD

AI summary

A lower layer of a microelectronic device may be patterned by forming a first sacrificial layer on the lower layer; patterning a plurality of spaced apart trenches in the first sacrificial layer; forming a second sacrificial layer in the plurality of spaced apart trenches; patterning the second sacrificial layer in the plurality of spaced apart trenches to define upper openings in the plurality of spaced apart trenches; and patterning the lower layer using the first and second sacrificial layers as a mask to form lower openings in the lower layer.