Silicon Dioxide Film Density via Krypton Sputtering

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Solution Overview

Problem

Conventional pulsed DC reactive sputtering and PECVD of silicon dioxide result in films with densities less than 2.30 g/cm³, limiting their acoustic and electrical performance, and there is a need for higher density films and improved fabrication throughput.

Innovation Solution

A method and apparatus using a sputtering gas mixture of oxygen and krypton with a krypton to oxygen ratio of 0.1-0.9 and applying RF power to the substrate for pulsed DC reactive sputtering, achieving silicon dioxide films with densities greater than 2.35 g/cm³ and improved deposition rates.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional pulsed DC reactive sputtering or PECVD is used to deposit silicon dioxide, then the deposition process can be performed, but the resulting films have low density (≤2.30 g/cm³) which limits acoustic and electrical performance

Engineering Contradiction:

Improvefilm densityVSAvoidacoustic and electrical performance

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent changes the sputtering gas composition from conventional argon-based mixtures to a krypton-oxygen mixture with specific ratios (0.1-0.9 Kr:O2). This parameter change in the gas chemistry enables the formation of high-density silicon dioxide films (≥2.35 g/cm³) with improved acoustic and electrical properties while maintaining the pulsed DC reactive sputtering process

Inventive Principle:

Principle #35Parameter changes

2Productivity

If conventional sputtering methods are used, then the process is relatively simple, but the deposition rate is slow and film density is limited to about 2.35 g/cm³ at best

Engineering Contradiction:

Improvedeposition rateVSAvoidfilm density

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent modifies the sputtering gas parameters by using krypton-oxygen mixtures at controlled ratios and pressures (1-20 mTorr), which simultaneously increases both the deposition rate and film density, overcoming the limitations of conventional argon-based sputtering methods

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs pulsed DC reactive sputtering with periodic pulsing of the sputtering process. This periodic action allows for better control of film formation, enabling higher density films to be deposited at improved rates by cycling between sputtering and oxidation phases

Inventive Principle:

Principle #19Periodic 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

The method produces high-density silicon dioxide films with densities up to 2.40 g/cm³ and higher refractive indices, enhancing acoustic and electrical performance, and significantly increasing deposition rates, making them suitable for advanced applications like SAW, BAW, and TCSAW filters.

Implementation Method 1

pulsed DC reactive sputtering of silicon dioxide

Methodology Applied

Scientific EffectSputtering: Sputtering

Implementation Method 2

deposit silicon dioxide thin films by thermal oxidation, plasma enhanced chemical vapour deposition (PECVD), reactive RF sputtering, and pulsed DC sputtering

Methodology Applied

Scientific EffectPhysical Vapour Deposition: Physical Vapour Deposition

Implementation Method 3

RF power is applied to the substrate to produce a DC bias. This can produce improved SiO2 density

Methodology Applied

Scientific EffectRF power to DC bias conversion:

Data Source

PatentUS9803272B2Deposition of silicon dioxide

Publication Date: 2017.10.31 SPTS TECH LTD

AI summary

According to the invention there is a method of depositing SiO2 onto a substrate by pulsed DC reactive sputtering which uses a sputtering gas mixture consisting essentially of oxygen and krypton.