Silicon Cleaning Solution Using Iodine Oxidizer and Buffer

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Solution Overview

Problem

Conventional cleaning solutions for silicon surfaces in semiconductor fabrication fail to effectively remove damaged portions and improve etch selectivity, particularly when dealing with silicon oxide layers like BPSG, leading to lattice defects and increased surface roughness, which affects the quality of thin films and contact resistance.

Innovation Solution

A cleaning solution comprising a buffer solution with acetic acid, ammonium acetate, iodine oxidizer, and hydrofluoric acid, with specific weight percentages and pH range, is used to selectively etch and remove damaged silicon surfaces while maintaining stable pH, thereby improving etch selectivity and reducing surface defects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional cleaning solutions (SC1 or dilute fluoric acid) are used, then the cleaning process can be performed, but the etch selectivity of silicon to silicon oxide layer deteriorates, causing insufficient cleaning effect

Engineering Contradiction:

Improvecleaning effectVSAvoidetch selectivity

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The invention changes the chemical parameters of the cleaning solution by introducing iodine oxidizer and adjusting the composition ratio of hydrofluoric acid, acetic acid, and ammonium acetate. This creates a new chemical environment that enables selective etching of damaged silicon surfaces while preserving the BPSG layer, resolving the contradiction between cleaning effectiveness and etch selectivity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The cleaning solution combines multiple chemical components (iodine oxidizer, hydrofluoric acid, acetic acid, ammonium acetate) into a composite formulation. Each component serves a specific function: iodine oxidizer for oxidation, hydrofluoric acid for etching, and acetic acid-ammonium acetate buffer for pH stabilization. This composite approach achieves both effective cleaning and maintained etch selectivity

Inventive Principle:

Principle #40Composite materials

2Manufacturing precision

If cleaning is performed to remove damaged silicon surface, then surface quality improves, but pH instability occurs during the cleaning process

Engineering Contradiction:

Improvesurface qualityVSAvoidpH stability

Core Design Contradiction:

Manufacturing precisionVSStability of the object's composition

Solution Approach 1:

The acetic acid-ammonium acetate buffer system acts as a chemical intermediary that stabilizes the pH environment during the cleaning process. This buffer system mediates between the acidic hydrofluoric acid and the oxidative iodine, maintaining pH stability that enables consistent cleaning performance and prevents unwanted side reactions

Inventive Principle:

Principle #24Intermediary (Mediator)

3Manufacturing precision

If strong etching is applied to remove damaged portions, then cleaning effectiveness improves, but surface roughness and lattice defects increase

Engineering Contradiction:

Improvecleaning effectivenessVSAvoidsurface roughness and lattice defects

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The cleaning solution exhibits local quality by selectively acting on damaged portions of the silicon surface while leaving intact areas unaffected. The iodine oxidizer specifically targets oxidized/damaged regions, and the hydrofluoric acid selectively etches these oxidized areas, achieving localized cleaning that removes contaminants without damaging the overall surface quality or creating lattice defects

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

The solution effectively removes damaged silicon surfaces, enhances etch selectivity, and stabilizes the pH, ensuring improved film quality and reduced surface roughness, even with weaker silicon oxide layers like BPSG, by using iodine oxidizer and hydrofluoric acid as etchant and acetic acid and ammonium acetate as a buffer.

Implementation Method 1

iodine oxidizer

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 2

hydrofluoric acid (HF)... as etchant

Methodology Applied

Scientific EffectChemical etching: Chemical Bonding

Implementation Method 3

a buffer solution including acetic acid (CH3COOH) and ammonium acetate (CH3COONH4)... having a pH that is stable in a cleaning process

Methodology Applied

Scientific EffectBuffer solution:

Data Source

PatentUS7449417B2Cleaning solution for silicon surface and methods of fabricating semiconductor device using the same

Publication Date: 2008.11.11 SAMSUNG ELECTRONICS CO LTD

AI summary

There are provided a cleaning solution for a silicon surface containing a buffer solution including acetic acid (CH3COOH) and ammonium acetate (CH3COONH4), iodine oxidizer, hydrofluoric acid (HF), and water. In a method for fabricating a semiconductor device, a silicon substrate may have an exposed silicon surface, which may be cleaned using a cleaning solution that contains a buffer solution including acetic acid and ammonium acetate, iodine oxidizer, hydrofluoric acid, and water.