Solidly Mounted Resonator (SMR)

Chloe Allison

Last edited December 06, 2019 12:10

In this tutorial we will learn how to simulate a 2D Solidly Mounted Resonator (SMR). We will analyse the maximum velocity and impedance of the device and the mode shapes.

You will learn:

The basic simulation workflow in OnScale Designer
How to set up a 2D model
How to create a simple geometry

How to duplicate geometries

How to pattern out geometry
How to use material copies for easy load assignment
How to display and post-process results

What is an SMR?: SMRs are a type of film bulk acoustic resonator for microwave operation applications and is usually a set of quarter wavelength thick layers attached to a substrate fabricated onto a the resonator.

Model Definition

Characteristics of the model

Model:	SMR
Mesh Size:	15 Elements per Wavelength
Analysis Time:	2.5 us
Output Results:	-Data Array of Maximum Y Velocity -Velocity Mode Shape at 2 GHz

Material Data

Name	Code Name	Density	Bulk Velocity	Shear Velocity	Poling
Aluminum Nitride	aln	3260 kg.m-3	-	-	Y+
Aluminium	alum	2690 kg.m-3	6306 ms-1	3114 ms-1	-
Silicon, Generic	si	2330 kg.m-3	7526 ms-1	4346 ms-1	-
Silicon Dioxide, Generic	sio2	2650 kg.m-3	5750 ms-1	2200 ms-1	-
Tungsten, Generic	tung	19400 kg.m-3	5200 ms-1	2900 ms-1	-
Aluminum Nitride (Copy)	aln	3260 kg.m-3	-	-	Y+

Note: All of these materials were taken from the Project Materials Database. However, aln2 is a copy of the material aln which is used to define a load across only half of the aluminium nitride layer.

Why This Simulation?

SMRs use acoustic mirrors (Bragg layers) typically to reduce substrate losses to maintain a high quality factor, a key performance metric for these types of filters. Simulation can be used to find a design which minimises these losses.

The simple 2D model consists of an Aluminum Nitride active layer on top multiples layers of Silicon Dioxide and Tungsten and Silicon substrate.

The Simulation Process

Let's go through the step by step tutorial and see how to simulate a 2D SMR in OnScale!

Step 1 - Create a New Project

Open up OnScale in Designer Mode. The first step is to create a new project.

In the Home tab of the ribbon, click New Project. The New Project window shows.
Type a name for the project.
If desired, change the save location and/or project file name by clicking … beside Project File.
For Analysis, select Mechanical Dynamic.
For Model Type, select 2D Model.
Select the Advanced checkbox.
For Distance, select μm.
Click OK.

Step 2 - Set the Frequency of Interest

First we will specify the frequency of interest.

Select Project Settings in the Model Tree
Expand the Frequency of Interest property
Tick the box
Enter a value of 2e9
Expand the Frequency of Damping property
Tick the box
Enter a value of 2e9

Step 3 - Add the Materials from the Material DB

The second step is to add the required materials for the SMR to the Project Materials database.

Aluminum Nitride

Add positively polled piezoelectric material.

Click Project Materials icon to open the Material Database
Expand the 'Piezoelectric' materials dropdown
Double click 'Aluminium Nitride- aln' to add this to Project Materials

Silicon / Silicon Dioxide

Add substrate material.

Expand the 'Misc' materials dropdown
Double click 'Silicon, generic - si' to add this to Project Materials
Double click 'Silicon Dioxide, generic - sio2' to add this to Project Materials

Tungsten

Now add the bragg layers material.

Expand 'Metal' materials dropdown
Double click on 'Tungsten, generic - tung' to add it to Project Materials

Aluminium Nitride (Copy)

Now copy AlN material.

Right click 'aln' and select Copy
Set Material Name to aln2
Select OK
Select Done

Step 4 - Create Basic Geometric Shapes

We will make use of the geometric primitives to build the SMR. The geometry consists of a silicon substrate, bragg layers and a resonator.

Substrate

We will start by creating the substrate.

Select the Rectangle primitive
Set the Material property of primitive_1 to si
Set the X End property to 100
Set the Y End property to 2

Bragg Layers

Next we will add geometry to represent the 5 Bragg layers.

Select the Rectangle primitive
Set the Material property of primitive_2 to tung
Set the Y Begin property to 2
Set the X End property to 100
Set the Y End property to 2.65
Set Pattern Type to Linear
Expand Num of Reps. and set X to 1
Set Y to 5
Expand Seperation Distance and set X to 0
Set Y to 1.39

Select the Rectangle primitive
Set the Material property of primitive_3 to sio2
Set the Y Begin property to 2.65
Set the X End property to 100
Set the Y End property to 3.39
Set Pattern Type to Linear
Expand Num of Reps. and set Y to 5
Expand Seperation Distance and set Y to 1.39

Aluminim Nitride Resonator

Having added the Bragg layers, lastly we need to add the piezoelectric layer to act as the resonator.

Select the Rectangle primitive
Set the Material property of primitive_4 to aln
Set the Y Begin property to 8.95
Set the X End property to 50
Set the Y End property to 11.7

Select the Rectangle primitive
Set the Material property of primitive_5 to aln
Set the X Begin property to 50
Set the Y Begin property to 8.95
Set the X End property to 100
Set the Y End property to 11.7

The resulting SMR geometry should be as follows:

Step 5 - Define a Time Function

The next step is to add a drive function. We will use a Ricker Wavelet function with a frequency of 2 GHz.

Click '+' to open the Drive Function dialogue
Change function type from Sinusoidal to Ricker Wavelet
Set Drive Frequency to 2e9
Click Insert to close the window. A record called timefunc_1 will be added to the Model Tree

Step 6 - Choose The Right Mesh Size

It is time to set up the meshing of the model.

Expand Model in the Model Tree
Expand Mesh
Select Configuration
Set Definitions to Advanced
Set Elements per Wavelength to 15
Expand Mesh Velocity
Set Value to 6000

Step 7 - Create Voltage Loads Across Piezo

We will now create two loads on each side of the aln material.

Create load 1

Expand Boundary Conditions and then, beside Loads, click +.
For Creation Mode, select Geometry Interface.
For Geometry, select primitive_4 (aln) or click it in the model.
For Interfacing Item, select side 4 (ymax).
For Load Type, select Voltage.
For Area Scaling, type 0.0002.
For Termination, select timefunc_1.
Click Create Load.

Create load 2

The Load Definition window should still be open.

For Geometry, select primitive_4 (aln) or click it in the model.
For Interfacing Item, select primitive 3 (sio2).
For Termination, select Ground.
Click Create Load.

Step 8 - Define the Boundary Conditions

We will now apply boundaries to the exterior surfaces of the SMR.

Click Domain Boundaries in the Model Tree
Set X Minimum to Symmetry
Set X Maximum to Impedance
Set Density to 3385
Set Longitudinal Velocity to 11099.6
Set Shear Velocity to 6012.87
Set Y Minimum to Impedance
Set Density to 3385
Set Longitudinal Velocity to 11099.6
Set Shear Velocity to 6012.87
Set Y Maximum to Free

Step 9 - Define Simulation Time

We will now set the model simulation time to be 2.5 us.

Click Analysis
Change Simulation Run Time to 2.5e-6

Step 10 - Define the Simulation Output Results

We will now define the 2 outputs we wish to see - data array of max velocity and a velocity mode shape at the center frequency.

Output Result 1 : Field Data Array of Maximum Velocity

Click '+' to create a new output
Set Output Type to Field Data
Set Array Type to Velocity
Set Array Component to Y
Set Field Type to Maximum

Output Result 2 : Velocity Mode Shape at Center Frequency

Click '+' to create a new output
Set Output Type to Shape Data
Set Array Type to Velocity
Set Array Component to Y
Set Frequency to 2e9

Step 11 - Run the Simulation on the Cloud

At this point the model is completely set up and it can now be run on the cloud.

Click Run on Cloud
Select Estimate
Select Run

How to Get the Simulation Results?

Once the simulation has finished, the results are available in your storage to download.

Click the Storage icon to open the cloud storage
Select your job from the dropdown menu
Expand the simulation folder
CTRL + select the -shape.flxdato, flxdato & flxhst file, right click and select Download Selection

Choose an appropriate save location and close the cloud storage.

Step 12 - Check the Simulation Results

Switch to the Post Processor

Click this icon to access the Post Processor to analyse simulation results

Open Results

Click File Explorer
Double click the -shape.flxdato to open the shape results
Double click the .flxdato file to open the data array results
Double click the history file to open the time history results

Velocity Mode Shape at Center Frequency

Expand Mode Shapes
Expand Mode-1
Right-click yvel and select Plot Shape Movie
In the Model Graphics tab, select Symmetry > About X
Set Scale Factor to 0.01
Select Play button to play mode shape animation

Data Array of Maximum Y Velocity

Expand Time-179652
Double click 'yvmx' to plot maximum velocity data field
Select Continue
Select Surface Plot
Rotate viewport to see suface plot of yvmx

Impedance

Select pize load1:Voltage
Select Impedance button
Double click Impd:load1.amp
Select Continue
Select Log yAxis
Set xAxis Minimum to 1.8e9
Set xAxis Maximum to 2.2e9

Try for Yourself

Now that we have introduced you to the tutorial, try have a play around with some of the settings, add some other outputs, or use this model as a starting point of your own.

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