Uniform Tunnel Insulation Structure for Flash Memory

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Solution Overview

Problem

Current flash memory devices face challenges in forming uniformly thick tunnel insulation layers due to substrate damage during etching, leading to increased threshold voltage distribution and charge trapping sites, which affect endurance and reliability.

Innovation Solution

A method involving multiple oxidation and nitration processes to form oxide and nitride layers with uniform thickness, using radical and thermal processes to create layers with controlled nitrogen distribution, reducing charge trapping sites and improving electrical characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If etching process is used to form tunnel insulation layer, then insulation layer can be formed, but substrate damage occurs leading to non-uniform thickness

Engineering Contradiction:

Improveuniformity of insulation layer thicknessVSAvoidsubstrate damage during etching

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the mechanical/chemical etching process with a thermal oxidation process to form the tunnel insulation layer. Instead of using etching chemicals that damage the substrate, the invention uses controlled thermal oxidation to grow the insulation layer in-situ, ensuring uniform thickness without substrate damage. This is evident in the method where a first oxidation process forms a preliminary oxide layer that is then converted to nitride and back to oxide, creating a uniform tunnel insulation layer.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Manufacturing precision

If multiple oxidation and nitration processes are used, then uniform insulation structure with controlled nitrogen distribution is achieved, but process complexity increases

Engineering Contradiction:

Improveuniformity of insulation layer thicknessVSAvoidnumber of process steps

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent combines multiple functions into integrated process steps. The first oxidation process simultaneously forms the preliminary oxide layer and prepares the substrate surface. The nitration process converts the oxide to nitride while maintaining uniform thickness. The second oxidation process then forms the final tunnel insulation layer. These combined steps achieve uniform insulation structures with controlled nitrogen distribution, reducing the need for separate intermediate processing steps.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent performs preliminary oxidation to form a preliminary oxide layer before converting it to nitride and then to the final oxide layer. This preliminary action ensures that the substrate is properly prepared and that the subsequent processes will produce a uniform tunnel insulation layer. The preliminary oxide layer serves as a template that guides the formation of the final uniform structure.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If conventional oxidation process is used, then insulation layer is formed, but charge trapping sites are generated affecting reliability

Engineering Contradiction:

Improveendurance and reliability of flash memory deviceVSAvoidcharge trapping sites in insulation layer

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent changes the chemical composition and structural parameters of the insulation layer by introducing nitrogen through the nitration process. The nitrogen atoms are distributed in a controlled manner within the oxide layer, creating an oxynitride structure that has different electrical properties than conventional oxide. This parameter change reduces charge trapping sites and improves reliability, as the nitrogen distribution modifies the band structure and reduces defect states that would otherwise trap charges.

Inventive Principle:

Principle #35Parameter changes

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 achieves a uniform insulation structure with enhanced electrical characteristics and improved endurance and reliability by minimizing substrate damage and charge trapping, suitable for use as tunnel or gate insulation layers in semiconductor devices.

Implementation Method 1

at least one oxide layers are formed on an object by at least one oxidation process

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 2

at least one nitride layer is formed from portions of the at least one oxide layer by at least one nitration process

Methodology Applied

Scientific EffectNitration: Nitriding

Data Source

PatentUS8481387B2Method of forming an insulation structure and method of manufacturing a semiconductor device using the same

Publication Date: 2013.07.09 SAMSUNG ELECTRONICS CO LTD

AI summary

In a method of forming an insulation structure, at least one oxide layer is formed on an object by at least one oxidation process, and then at least one nitride layer is formed from the oxide layer by at least one nitration process. An edge portion of the insulation structure may have a thickness substantially the same as that of a central portion of the insulation structure so that the insulation structure may have a uniform thickness and improved insulation characteristics. When the insulation structure is employed as a tunnel insulation layer of a semiconductor device, the semiconductor device may have enhanced endurance and improved electrical characteristics because a threshold voltage distribution of cells in the semiconductor device may become uniform.