Recessed Access Gate Elevation Control via Sidewall Spacer Masks

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Solution Overview

Problem

Existing methods for forming recessed access device and isolation gate constructions in integrated circuitry often result in significant elevational variations of conductive surfaces within semiconductor material, leading to inconsistencies in device performance and reliability.

Innovation Solution

The method involves using anisotropically etched sidewall spacers to form precise mask openings for etching recessed access device and isolation trenches, ensuring that all recessed access device gate constructions have elevationally outermost conductive surfaces within no greater than 50 Angstroms of the semiconductor material's thickness, and all isolation gate constructions have elevationally innermost surfaces within no greater than 40 Angstroms, thereby maintaining uniformity and consistency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional methods are used to form recessed access device and isolation gate constructions, then device fabrication can be completed, but significant elevational variations of conductive surfaces occur leading to inconsistencies in device performance and reliability

Engineering Contradiction:

Improveelevational positioning of conductive surfacesVSAvoiddevice performance consistency

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent introduces sidewall spacers as intermediary structures that define the boundaries for etching recesses and isolation regions. These spacers act as precise masks that control the lateral dimensions and elevational positioning of conductive surfaces, ensuring uniformity across all devices in the array. The spacers are formed with controlled thickness and positioning, which directly determines the elevational alignment of gate constructions.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent employs selective etching parameters and deposition conditions to control the elevational positioning of conductive surfaces. By adjusting etch depth, deposition thickness, and annealing conditions, the method achieves precise control over the relative elevations of recessed access device gates and isolation gates, maintaining variations within 50 Angstroms as specified.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If precise elevational control is achieved through multiple processing steps, then manufacturing precision improves, but fabrication process complexity increases

Engineering Contradiction:

Improveelevational uniformity of conductive surfacesVSAvoidfabrication process steps

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent combines the formation of recesses and isolation regions into a single etching step using a common mask layer defined by sidewall spacers. This merged approach achieves precise elevational control for both structures simultaneously, reducing the total number of processing steps compared to forming them separately with different masks and etch conditions.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The sidewall spacers are formed in advance before the etching of recesses and isolation regions. This preliminary formation of precise masks allows subsequent etching steps to achieve accurate elevational positioning without requiring additional alignment or mask preparation steps, simplifying the overall fabrication sequence.

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

This approach ensures uniform elevational positioning of conductive surfaces, enhancing the reliability and performance of recessed access devices and isolation gate constructions by minimizing elevational variations, which can improve the overall functionality and consistency of integrated circuitry.

Implementation Method 1

using anisotropically etched sidewall spacers to form precise mask openings for etching recessed access device and isolation trenches

Methodology Applied

Scientific EffectAnisotropic etching:

Data Source

PatentUS9385132B2Arrays of recessed access devices, methods of forming recessed access gate constructions, and methods of forming isolation gate constructions in the fabrication of recessed access devices

Publication Date: 2016.07.05 MICRON TECHNOLOGY INC

AI summary

A method of forming an array of recessed access device gate constructions includes using the width of an anisotropically etched sidewall spacer in forming mask openings in an etch mask for forming all recessed access device trenches within semiconductor material within all of the array. The etch mask is used while etching all of the recessed access device trenches into the semiconductor material within all of the array through the mask openings. Individual recessed access gate constructions are formed in the individual recessed access device trenches. Other methods are contemplated, including arrays of recessed access devices independent of method of manufacture.