ScAlN Sputter Deposition with Two-Stage Gas Control

Solution Overview

Problem

Existing methods for depositing additive-containing aluminium nitride films struggle to maintain low defect density and high electromechanical coupling coefficient (Keff) as the additive element concentration increases, particularly above 8 At %, which is necessary for manufacturing high-quality RF resonator devices.

Innovation Solution

A two-step pulsed DC reactive sputtering method is employed, where the first layer is deposited in a highly nitrogen-rich or nitrogen-only atmosphere to reduce defect formation, followed by a second layer deposited in a mixture of nitrogen and an inert gas, optimizing the nitrogen gas flow rates and inert gas composition to achieve improved crystallinity and texture.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the amount of additive element in additive-containing aluminium nitride is increased to improve electromechanical coupling coefficient, then the electromechanical coupling coefficient increases, but crystallographic defects increase and film quality deteriorates

Engineering Contradiction:

Improveelectromechanical coupling coefficientVSAvoidcrystallographic defect density

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The deposition process is divided into two distinct stages: a first deposition stage using a nitrogen-rich atmosphere to grow the initial film layer, and a second deposition stage using a different gas composition to complete the film. This segmentation allows each stage to be optimized for different objectives - the first stage focuses on reducing defects while the second stage completes the film with desired properties, thereby achieving high additive content without proportionally increasing defect density

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The gas composition parameter is dynamically changed during the deposition process. The first stage uses a nitrogen-rich atmosphere (high nitrogen to inert gas ratio), and the second stage uses a different gas composition. This parameter change enables control over the deposition kinetics and film formation mechanisms, allowing high additive element incorporation while maintaining low defect density through optimized nucleation and growth conditions

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If conventional single-stage deposition is used, then the process is simple, but defect density increases and film texture deteriorates at high additive concentrations

Engineering Contradiction:

Improvedeposition process simplicityVSAvoidfilm texture quality

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The deposition process is divided into two distinct stages: a first deposition stage using a nitrogen-rich atmosphere to grow the initial film layer, and a second deposition stage using a different gas composition to complete the film. This segmentation allows each stage to be optimized for different objectives - the first stage focuses on reducing defects while the second stage completes the film with desired properties, thereby achieving high additive content without proportionally increasing defect density

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The gas composition parameter is dynamically changed during the deposition process. The first stage uses a nitrogen-rich atmosphere (high nitrogen to inert gas ratio), and the second stage uses a different gas composition. This parameter change enables control over the deposition kinetics and film formation mechanisms, allowing high additive element incorporation while maintaining low defect density through optimized nucleation and growth conditions

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

This method effectively reduces defect density and improves the texture and crystallinity of additive-containing aluminium nitride films, allowing for higher additive element concentrations while maintaining acceptable levels of defect density and electromechanical coupling efficiency.

Implementation Method 1

a first layer of the additive-containing aluminium nitride film is sputter deposited onto a substrate disposed within a chamber

Methodology Applied

Scientific EffectSputtering: Sputtering

Implementation Method 2

by pulsed DC reactive sputtering

Methodology Applied

Scientific EffectPlasma: Plasma

Data Source

PatentUS12207556B2Method of deposition

Publication Date: 2025.01.21 SPTS TECH LTD

AI summary

In a method for sputter depositing an additive-containing aluminium nitride film containing an additive element like Sc or Y, a first layer of the additive-containing aluminium nitride film is deposited onto a substrate disposed within a chamber by pulsed DC reactive sputtering. A second layer of the additive-containing aluminium nitride film is deposited onto the first layer by pulsed DC reactive sputtering. The second layer has the same composition as the first layer. A gas or gaseous mixture is introduced into the chamber when depositing the first layer. A gaseous mixture comprising nitrogen gas and an inert gas is introduced into the chamber when depositing the second layer. The percentage of nitrogen gas in the flow rate (in sccm) when depositing the first layer is greater than that when depositing the second layer.