Single-Wafer Cluster Tool Tunnel Oxide Fabrication

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Solution Overview

Problem

Conventional batch processing methods for scaling tunnel oxide layers in non-volatile semiconductor memories result in poor quality and non-uniformity, due to variations in wafer arrangement and thermal budget constraints.

Innovation Solution

A single-wafer cluster tool is used to form a tunnel dielectric layer at higher temperatures, reducing thermal impact and achieving high-quality, thin tunnel dielectric layers with reduced hydrogen content, and the entire ONO stack is fabricated in a single pass to preserve pristine interfaces between layers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If batch processing equipment is used to grow tunnel oxide layer, then multiple wafers can be processed simultaneously, but tunnel oxide layer quality and thickness uniformity deteriorate due to wafer arrangement variations and thermal budget constraints

Engineering Contradiction:

Improvenumber of wafers processed simultaneouslyVSAvoidtunnel oxide layer thickness uniformity

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The batch processing system is segmented into multiple single-wafer processing chambers arranged in a cluster configuration. Each chamber processes one wafer at a time through controlled thermal zones, eliminating the thermal interference and positioning variations inherent in batch processing while maintaining high throughput through continuous wafer circulation among chambers.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention transitions from processing multiple wafers in the same spatial plane (batch mode) to processing wafers sequentially through multiple spatial dimensions (cluster of chambers). Wafers move through a defined path across multiple chambers, each optimized for specific processing conditions, thereby achieving both high productivity and precise thickness control.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Length of moving object

If batch processing is used to grow thinner tunnel oxide layers, then device scaling is enabled, but tunnel oxide layer quality becomes unacceptably low

Engineering Contradiction:

Improvetunnel oxide layer thicknessVSAvoidtunnel oxide layer quality

Core Design Contradiction:

Length of moving objectVSReliability

Solution Approach 1:

The invention changes the processing parameters by maintaining higher temperatures (900-1100°C) in the oxidation chambers compared to conventional batch processing. This temperature parameter change enables the growth of thinner tunnel oxide layers with superior quality, as the higher thermal energy promotes better oxide formation kinetics and reduces defects even at reduced thicknesses.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The single-wafer cluster tool enables continuous processing where wafers move through oxidation, deposition, and annealing chambers in sequence without breaking vacuum or exposing to atmosphere. This continuous action prevents contamination and thermal cycling that would degrade oxide quality, enabling reliable thin oxide layer formation.

Inventive Principle:

Principle #20Continuity of useful action

3Stability of the object's composition

If long temperature ramp times are used in batch oxidation chamber, then thermal stabilization is achieved, but thermal budget of wafers is reduced

Engineering Contradiction:

Improvethermal stabilizationVSAvoidthermal budget

Core Design Contradiction:

Stability of the object's compositionVSLoss of time

Solution Approach 1:

Each wafer undergoes preliminary thermal stabilization in its own dedicated chamber before entering the oxidation process. The individual chamber pre-heats the wafer to the required temperature, eliminating the need for long ramp times in batch processing. This preliminary action ensures thermal stability is achieved quickly without consuming excessive thermal budget from subsequent processing steps.

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 allows for scalable non-volatile charge trap memory devices with improved tunnel dielectric layer quality and reduced thickness variability, enhancing performance and uniformity without degrading the thermal budget.

Implementation Method 1

a tunnel dielectric layer is formed on a substrate in a first process chamber of a single-wafer cluster tool

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 2

A single-wafer cluster tool is used to form a tunnel dielectric layer at higher temperatures, reducing thermal impact

Methodology Applied

Scientific EffectThermal processing: Heating

Data Source

PatentUS7670963B2Single-wafer process for fabricating a nonvolatile charge trap memory device

Publication Date: 2010.03.02 LONGITUDE FLASH MEMORY SOLUTIONS LTD

AI summary

A method for fabricating a nonvolatile charge trap memory device is described. The method includes first forming a tunnel dielectric layer on a substrate in a first process chamber of a single-wafer cluster tool. A charge-trapping layer is then formed on the tunnel dielectric layer in a second process chamber of the single-wafer cluster tool. A top dielectric layer is then formed on the charge-trapping layer in the second or in a third process chamber of the single-wafer cluster tool.