Low pH Fluorine Cleaning Solution for Semiconductor Oxide Removal

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Solution Overview

Problem

Conventional cleaning solutions used in semiconductor fabrication, such as ultradilute hydrofluoric acid, effectively remove native oxide from substrates but also laterally etch dielectric materials, widening openings and increasing the risk of shorts between conductive elements.

Innovation Solution

A low pH, fluorine-containing solution comprising water, hydrofluoric acid, and a strong acid like hydrochloric acid is used to selectively remove native oxide from semiconductor structures without substantially etching dielectric materials, maintaining the critical dimension of openings and improving contact resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional cleaning solutions (ultradilute HF) are used to remove native oxide, then native oxide removal is effective, but dielectric material is laterally etched causing opening widening

Engineering Contradiction:

Improvenative oxide removal effectivenessVSAvoidopening critical dimension control

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent changes the chemical parameters of the cleaning solution by using low pH (0.5-2.0) fluorine-containing solutions with specific concentrations (e.g., 0.1-10% NH4F, 0.01-1% HF) instead of conventional ultradilute HF. This parameter change enables selective oxide removal while minimizing dielectric etching, resolving the contradiction between cleaning effectiveness and dimensional control

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces ammonium fluoride (NH4F) as an intermediary substance that enhances the cleaning mechanism. NH4F acts as a buffer and provides controlled fluoride ion release, enabling effective oxide removal through intermediary chemical reactions while reducing direct aggressive HF attack on dielectric materials, thus preventing opening widening

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If HF concentration is increased to improve oxide removal speed, then cleaning efficiency increases, but dielectric material etching increases

Engineering Contradiction:

Improveoxide removal speedVSAvoiddielectric material etching

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent optimizes the concentration parameters of fluoride compounds to achieve balanced performance. By using low concentrations (0.1-10% NH4F, 0.01-1% HF) combined with low pH conditions, the solution achieves adequate oxide removal speed while minimizing dielectric etching, resolving the contradiction between productivity and harmful effects

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite cleaning solution system combining multiple components (NH4F, HF, HCl, H2O) in specific ratios. This composite formulation provides synergistic effects where NH4F buffers the aggressive HF, enabling controlled oxide removal at optimized speeds while protecting dielectric materials from excessive etching

Inventive Principle:

Principle #40Composite materials

3Reliability

If opening diameter is increased due to lateral etching, then oxide removal is more complete, but short risk between conductive elements increases

Engineering Contradiction:

Improveoxide removal completenessVSAvoidshort risk between conductive elements

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent uses low pH and controlled fluoride concentration parameters to achieve complete oxide removal without lateral dielectric etching. This maintains the original opening dimensions while ensuring thorough oxide removal, eliminating the need to increase opening diameter and thus preventing short risks between conductive elements

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 low pH, fluorine-containing solution effectively removes native oxide without significantly widening the openings, reducing the risk of shorts and improving contact resistance between substrates and contact plugs, while also preventing native oxide regrowth, thus enhancing the reliability and efficiency of semiconductor device fabrication.

Implementation Method 1

The cleaning process may include a cleaning solution, such as at least one of QEII, MSe2, and ultradilute hydrofluoric acid (1000 parts water to 1 part HF). Either through immersion, spraying, vapor treatment, or other methods, the native oxide of the in-process device is exposed to and removed by the cleaning solution.

Methodology Applied

Scientific EffectChemical etching:

Implementation Method 2

Methodology Applied

Scientific EffectSelective etching:

Data Source

PatentUS8546016B2Solutions for cleaning semiconductor structures and related methods

Publication Date: 2013.10.01 MICRON TECHNOLOGY INC

AI summary

A method for cleaning a semiconductor structure includes subjecting a semiconductor structure to an aqueous solution including at least one fluorine compound, and at least one strong acid, the aqueous solution having a pH of less than 1. In one embodiment, the aqueous solution includes water, hydrochloric acid, and hydrofluoric acid at a volumetric ratio of water to hydrochloric acid to hydrofluoric acid of 1000:32.5:1. The aqueous solution may be used to form a contact plug that has better contact resistance and improved critical dimension bias than conventional cleaning solutions.