Buried Plate Uniformity in DRAM Trenches via Arsenic Vapor Deposition

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Solution Overview

Problem

Buried plate electrodes in high aspect ratio trenches of DRAM devices face challenges in achieving uniform arsenic coverage due to limitations in spin-on-glass deposition and ion implantation methods, which result in inadequate coverage and non-uniformity, especially with interlevel dielectric layers present.

Innovation Solution

Applying an arsenic-containing gas to the trench sidewalls to deposit an arsenic-containing layer, followed by an encapsulating material and an anneal process to drive arsenic into the substrate, ensuring complete sidewall coverage and uniformity of the buried plate electrode.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If spin-on-glass deposition or ion implantation is used to form buried plate electrode, then the process can be completed, but uniform arsenic coverage is not achieved especially in high aspect ratio trenches

Engineering Contradiction:

Improveuniformity of arsenic coverageVSAvoidprocess complexity

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

An arsenic-containing layer is deposited as an intermediary material on the trench sidewalls, which then serves as a source for arsenic diffusion into the semiconductor substrate. This intermediary layer enables uniform arsenic distribution without requiring direct spin-on-glass deposition or ion implantation into the deep trench, resolving the coverage uniformity issue while maintaining process feasibility

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces mechanical deposition methods (spin-on-glass) and ion implantation with a chemical vapor deposition approach followed by thermal diffusion. The arsenic-containing layer is deposited via CVD and then arsenic is driven into the substrate through thermal annealing, substituting mechanical processes with chemical and thermal processes to achieve better uniformity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If conventional deposition methods are used, then the process is simpler, but coverage is inadequate in high aspect ratio trenches

Engineering Contradiction:

Improvecoverage completenessVSAvoidnumber of process steps

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The arsenic-containing layer is deposited on the trench sidewalls before the actual buried plate electrode formation. This preliminary deposition ensures that arsenic is already in position and will diffuse uniformly during subsequent annealing, achieving complete coverage in high aspect ratio trenches while managing process complexity through staged execution

Inventive Principle:

Principle #10Preliminary action

3Manufacturing precision

If arsenic is driven into substrate to form buried plate electrode, then functional electrode is created, but uniform concentration throughout electrode is difficult to achieve

Engineering Contradiction:

Improveuniformity of arsenic concentrationVSAvoidanneal temperature control

Core Design Contradiction:

Manufacturing precisionVSTemperature

Solution Approach 1:

The arsenic-containing layer is deposited conformally on the trench sidewalls, creating a localized arsenic source that distributes arsenic uniformly as it diffuses into the substrate. This local placement of arsenic ensures uniform concentration in the resulting buried plate electrode, with the uniformity controlled by the conformal deposition quality rather than difficult temperature control

Inventive Principle:

Principle #3Local quality

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 method provides complete and uniform arsenic coverage across the trench sidewalls, enhancing the performance and reliability of the buried plate electrode in high aspect ratio trenches.

Implementation Method 1

exposing the sidewalls of the trench to an arsenic-containing gas to deposit an arsenic containing layer on the sidewalls of the trench

Methodology Applied

Scientific EffectVapor deposition: Physical Vapour Deposition

Implementation Method 2

The arsenic from the arsenic-containing layer is driven into the semiconductor substrate to form a lower plate electrode

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS8563446B2Technique to create a buried plate in embedded dynamic random access memory device

Publication Date: 2013.10.22 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A method for forming a trench structure is provided for a semiconductor and/or memory device, such as an DRAM device. In one embodiment, the method for forming a trench structure includes forming a trench in a semiconductor substrate, and exposing the sidewalls of the trench to an arsenic-containing gas to adsorb an arsenic containing layer on the sidewalls of the trench. A material layer is then deposited on the sidewalls of the trench to encapsulate the arsenic-containing layer between the material layer and sidewalls of the trench.