AMB2022-07 Benchmark Measurements and Challenge Problems – PDF Copy

AMB2022-07 Benchmark Measurements and Challenge Problems

Modelers are invited to submit simulation results for any challenges they like before the deadline of

23:59 (ET) on July 15, 2022. Tabulated results using the challenge-specific templates are required for

most challenge problems and simulation results may be submitted here. An informational webinar for

AMB2022-07 will be held on May 6, 2022, from 12:15 – 13:15 Eastern Time. The webinar registration link

is here. After the webinar is completed, links to the recorded presentations and to a FAQ page will be

added to the AMB2022-07 description page. Additional information may become available later so

updated versions of this document may be posted. Please check back occasionally.

All evaluations of submitted modeling results will be conducted by the AM-Bench 2022 organizing

committee. Award plaques will be awarded at the discretion of the organizing committee. Because

some participants may not be able to share proprietary details of the modeling approaches used, we are

not requiring such details. However, whenever possible we strongly encourage participants to include

with their submissions a .pdf document describing the modeling approaches, physical parameters, and

assumptions used for the submitted simulations.

Please note that the challenge problems reflect only a small part of the validation measurement data

provided by AM Bench for each set of benchmarks. The Measurement Description section, below,

describes the full range of measurements conducted.

AMB2022-07: Vat Photopolymerization Measurements of Cure Depth and Print Fidelity Vs. Varied

Exposure Duration, Photopattern Dimensions, and Resin Characteristics

Detailed descriptions are found below, and simulation results may be submitted here.

● Optical profile at print plane (CHAL-AMB2022-07-OP): Light intensity profile at the print plane.

● Cure depth dependence on photomask dimensions (CHAL-AMB2022-07-CD): Cure depth as a

function of photomask linewidth and resin characteristics.

● Print profile (CHAL-AMB2022-07-PP): Solid cross section profile of the printed patterns as a

function of photomask linewidth and resin characteristics.

1. Overview and Basic Objectives

2. Printing and Post-Processing Description

3. Measurement descriptions

4. Benchmark Challenge Problems

5. Data to be Provided

6. Relevant References

______________________________________________________________________________

1. Overview and Basic Objectives

This Photopolymer AM-Bench 2022 Challenge is to accurately model the relationship between

photopattern exposure duration and resultant single-layer part dimension (i.e. fidelity and cure depth)

for four resins, which serve to orthogonally probe the relationship between resin reactivity k and
AMB2022-07 Benchmark Measurements and Challenge Problems – PDF Copy

viscosity ν. The primary objectives are to determine if the dimensions of a photomask and resin viscosity

and reactivity affect cure depth and print fidelity. Ultimately, the improved understanding and prediction

of these relations will foster enhanced print resolution and part performance.

Experimental data for model calibration and challenge comparison is provided through cure profile

measurements using laser confocal scanning microscopy in conjunction with resin characterization (i.e.

Fourier transform infrared spectroscopy, oscillatory rheometry) and system calibration (e.g., photomask

dimensions, beam profilometry, radiometry). These experiments were carried out at the National

Institute of Standards and Technology and the University of Colorado. Released calibration

measurements were performed on four, open-source resins to serve as representative examples for

resins in the field. Calibration data are available for download here.

2. Printing and Post- Processing Description

2.1. Materials and Sample Preparation

2.1.1. Resin Formulation

Acrylates and methacrylates are known to have different polymerization rates. In order to develop two

resins of equal viscosity, with different polymerization rates, methacrylate based and acrylate based

resins with viscosities of ≈150 mPa*s and ≈85 mPa*s were formulated.

The following materials were used in the formulations of the four resins:

Acrylate monomers: Bisphenol A glycerolate (1 glycerol/phenol) diacrylate (BisGA, Sigma Aldrich, CAS#

4687-94-9, Mw = 484.54 g/mol), isobornyl acrylate (IBA, Sigma Aldrich, CAS# 5888-33-5 607-133-00-9,

Mw = 208.30 g/mol), and trimethylolpropane triacrylate (TMPTA), Sigma Aldrich, CAS# 15625-89-5, Mw =

296.32 g/mol)

Methacrylate monomers: Bisphenol A glycerolate dimethacrylate (glycerol/phenol 1) (BisGMA, Sigma

Aldrich, CAS# 1565-94-2, Mw = 512.59 g/mol), isobornyl methacrylate (IBMA, Sigma Aldrich, CAS#

7534-94-3, Mw = 222.32 g/mol), trimethylolpropane trimethacrylate(TMPTMA, Sigma Aldrich, CAS#

3290-92-4, Mw = 338.40 g/mol).

Photoinitiator: Diphenyl(2,4,6-trimethylbenzoyl)-phosphine Oxide (TPO, TCI Chemicals CAS# 75980-60-8,

Mw = 348.38 g/mol)

The bisphenol based di-functionalized monomers have very high viscosities, so lower viscosity

comonomers were employed to bring viscosities down to our targeted range appropriate for 3D printing.

Isobornyl acrylate/methacrylate and trimethylolpropane triacrylate/trimethacrylate were used as the

lower viscosity comonomers and the tri-functionalized monomers allowed for high reactivity, respective

to the other monomers, while the acrylates exhibited the higher reactivity relative to the methacrylates.

Many common 3D printers use a 405 nm light to initiate photopolymerization so TPO at 1 wt% was

selected as the photoinitiator for these formulations. Resins were mixed by selecting a 10 gram basis and

initially weighing out the high viscosity bisphenol based monomers, followed by the addition of the

lower viscosity isobornyl and trimethylolpropane based monomers (by mass). The resin formulations

were mixed in a 45 °C water bath until the formulations were homogeneous. Finally, the TPO

photoinitiator was added and mixed at room temperature until fully dissolved.
AMB2022-07 Benchmark Measurements and Challenge Problems – PDF Copy

For the high reactivity, acrylate-based resins, the BisGA was diluted with IBA and TMPTA to bring the

viscosity down to the targeted range of ≈150 mPa*s. For the lower viscosity, ≈85 mPa*s, acrylate-based

resin, the BisGA content was reduced and supplemented with IBA to reduce the viscosity to the target

value. For the relatively lower reactivity, methacrylate-based resins, BisGMA was diluted with IBMA and

TMPTMA at different weight ratios to bring the viscosities down to the targeted range of ≈150 mPa*s

and ≈85 mPa*s.

Table 1: Resin composition broken down into respective reactivities, viscosities, and components

2.1.2. Sample substrate preparation

All samples were fabricated using methacrylate-functionalized 140 μm thick coverglass (Sigma Aldrich) as

a substrate/window to ensure the pattern polymerized to the desired substrate. The functionalization

procedure is as follows:

● Mix ethanol (95 % by volume) with deionized water (5 % by volume)

● Add acetic acid (Sigma Aldrich) to lower pH to between 4.5-5.5

● Remove desired amount from stock solution and place into coating beaker

● Add 3-(trimethoxysilyl)propyl methacrylate) (Sigma Aldrich) (2 % by volume)

● Mix using magnetic stir bar at 200 RPM for 30 min

● Clean coverglass by rinsing in pure ethanol for 10 minutes

● Place cleaned coverglass immediately into vial of methacrylate solution for 20 min

● Remove coverglass from solution, rinse with approximately 3 mL ethanol to remove excess

silane, and dry using air gun

● Thermally cure coverglass for 10 min at 110 °C for 10 min to cure methacrylate functionalization

● Mechanically clean coverglass to remove remaining, untethered silane

o Deposit ethanol onto coverglass, rub front and back surface of coverglass between index

and forefinger in circular patterns using lens paper for 10 seconds

o Repeat rubbing procedure for 10 seconds using new, dry lens paper

2.2. Light Engine

The light engine is comprised of a high-power, collimated 405 nm LED (Thorlabs, SOLIS-405C), a

graduated iris aperture (Thorlabs, SM1D12C), and a chrome photomask (Edmund Optics, high precision

Ronchi ruling), illustrated in Figure 1.
AMB2022-07 Benchmark Measurements and Challenge Problems – PDF Copy

Figure 1: Projection light engine used for all photopatterned exposures with an expanded schematic of

the sample setup.

2.2.1. Light source

A high-power, collimated 405 nm LED was used for all photopatterning (Thorlabs, SOLIS-405C). The light

engine uniformity and intensity were measured using beam profilometry and radiometry, respectively.

Additional manufacturer specifications for the light source are listed in Table 2.
AMB2022-07 Benchmark Measurements and Challenge Problems – PDF Copy

Table 2: Specification provided by Thorlabs for SOLIS-405C LED

(https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=8986&pn=SOLIS-405C).

2.2.2. Aperture

A ring actuated, graduated iris was used to define the edge boundaries of the aperture, which can be

locked to a set aperture dimension. The aperture functions as a hard, zero-transmission boundary for

photopatterning. A 3 mm aperture and 2 mm aperture were used for the cure depth calibration dataset

and solution dataset, respectively.

2.2.3. Photomask

Ronchi ruling photomasks (Edmund Optics) were used for all experiments. The patterns are comprised of

vacuum-deposited chrome (nominal optical density (OD) ≅ 3.0) on float glass (nominal thickness ≅ 1.5

mm). The masks are 25.4 mm x 25.4 mm overall lateral dimension, with the pattern repeated

periodically across the surface. The pattern dimensions are defined by line-pairs-per-inch (LPPI), which

can be converted to nominal line width by assuming a 50 % duty cycle of mask/un-mask. Nominal

linewidth dimensions are listed in Table 3.

True optical density can be calculated for each specific pattern using the chrome thickness measured by

atomic force microscopy for each photopattern. Modelers may also incorporate the float glass thickness

data measured with ± 10 μm accuracy, measured by digital calipers. Measured lateral dimensions of

photomask features were measured by Laser Scanning Confocal Microscopy.
AMB2022-07 Benchmark Measurements and Challenge Problems – PDF Copy

Table 3: Manufacturer-specified photomask linewidths with designated identifier, line-pairs-per-inch

(LPPI), and the subsequent conversion from LPPI to nominal micrometers per line (assuming 50 % duty

cycle).

2.3. Printing process

All samples were printed using the following procedure:

● Deposit index matching immersion oil (Sigma Aldrich, index of refraction = 1.52) onto back

surface of clean coverglass

● Place photomask directly on top of oil with chrome surface contacting the oil

● Lay lens paper onto to surface of photopattern and then place 1 kg aluminum weight onto

pattern and wait 1 minute to ensure uniform oil thickness layer

● Deposit resin solution onto neutral density filter (ThorLabs, Optical Density = 3.0) between two

shims (0.45 mm for the solution dataset and 1.25 mm for the calibration dataset) until resin fills

entire volume between shims and coverglass substrate (approximately 350 μL (solution dataset)

and 1 mL (calibration dataset))

● Place coverglass-photomask system directly onto open resin surface with clean coverglass

contacting the open resin, ensuring no air bubbles formed in resin during lamination

● Place entire sample system into the light engine photopatterning apparatus described in Section

2.2

● Translate sample vertically until at photopatterning location (where focus calibration

measurements were taken)

● Begin photopatterning for pre-defined exposure durations, translating the x and y actuators to

polymerize new locations within the single slide

● Once photopatterning complete, remove sample from system

2.4 Post-processing

All samples were post-processed using the following procedure:

● Remove Ronchi ruling photomask from back surface of coverglass by sliding the mask along the

narrow dimension of the coverglass until removed, holding tension at the shim locations to

ensure the coverglass does not shift on the ND filter + shim system

● Gently slide photo-patterned coverglass from ND filter + shim system to obtain resin-encased

prints

● Remove immersion oil from the back surface of the coverglass by applying IPA with lens paper
AMB2022-07 Benchmark Measurements and Challenge Problems – PDF Copy

● Place sample vertically into tissue-lined, light-tight sample holder container to allow excess resin

to drip and wick from substrate for between 2 h and 5 h

● Remove monomer-soaked tissue and place entire sample holder into volume of IPA and mix

system at 100 rpm for 45 minutes using a magnetic stir bar (ensuring stir bar does not directly

contact/agitate sample holder)

● Remove sample holder from IPA bath and gently rinse each sample using IPA and placing a tissue

at the edge of the slide to wick away remaining IPA

● Place sample into UV post cure oven for 30 minutes (now ready for characterization)

2.5 Specimen Naming Convention

All specimens were named using the following convention:

AMB2022-07_{experiment date}_{resin used}-{ν}{k}_{Ronchi ruling used}_{exposure time}_{specimen

slide number}_{row number}_ {column number}

Here, AMB2022-07 is for Additive Manufacturing Benchmarks 2022 Challenge Problem 7 and the

bracketed regions indicate a specific, unique identifier for the specimen. For example, a specimen made

on February 18, 2022 using Resin 1 (which has high viscosity and low reactivity ranking), the 300 LPPI,

and a 1 s (1000 ms) exposure with the slide number 3 would go as follows:

AMB2022-07_2022-02-18_Re1-HL_1000ms_300LPPI_3_r1_c2

An example specimen is shown in Figure 2 to demonstrate the definition of rows and columns.

Figure 2: Illustration of an exemplary photopatterned exposure dataset with the associated rows and

columns defined and the corresponding center-to-center photopattern separation distances. Columns

are exposure replicates and rows are variations in exposure duration.

3. Measurement Descriptions
AMB2022-07 Benchmark Measurements and Challenge Problems – PDF Copy

The AMB2022-07 benchmark elucidates fundamentals of vat photopolymerization additive

manufacturing by measuring the shape of patterned features subject to varying exposure duration,

photomask dimensions and resin characteristics. The calibration data seek to provide the most essential

properties to predict the profile of the photopattern and the dominant properties of the resin. The data

also provide phenomenological characteristics such as the working curve and associated critical exposure

dose and depth of polymerization. These working curve raw data obtained on ≈500 μm wide masked

features also provide insight into the real, non-rectangular profiles of the progressing cure front. The

measurements include:

Resin Characterization

● Fourier transform infrared spectroscopy measurements of polymer conversion vs

exposure duration for a constant exposure intensity

● Oscillatory rheometry measurements of resin viscosity prior to exposure

Light Engine Characterization

● Dimensional measurements of the chrome photomasks using laser scanning confocal

microscopy and atomic force microscopy

● Radiometric measurements of the LED light source to determine optical power

● Beam profile measurements at the print plane to determine uniformity of the

illumination

Printed Feature Characterization

● Laser scanning confocal microscopy measurements of printed patterns as calibration

data using ≈500 μm photomasks and as solution data using the other photomask sizes

3.1. Resin Characterization

3.1.1. Resin Reactivity: Fourier Transform Infrared Spectroscopy (FTIR)

Fourier-Transform Infrared Spectroscopy was conducted using a Thermo Fisher Nicolet 6700 FT-IR. The

acrylate/methacrylate peak at 6167 cm

-1 was monitored for double bond conversion to determine the

kinetics of curing. Experimental parameters are as shown in Table 4.

Spacers of 800 μL thickness were punched with a 12 mm diameter hole-punch. The resins were then

filled into the spacers and sandwiched between glass slides to eliminate the potential for oxygen

inhibition. Resins were then placed in the spectrometer and the kinetic runs were started, monitoring

the 6167 cm

-1 peak with a sampling interval of 0.52 s and a resolution of 4 cm-1

. An EXFO Acticure 4000

spot curing lamp with a 405 nm filter at 1 mW cm

-2 was employed for photocuring and at the 30 s time

point, the lamp was switched on and reduction in peak area, corresponding to double bond

acrylate/methacrylate conversion was monitored.
AMB2022-07 Benchmark Measurements and Challenge Problems – PDF Copy

Table 4: FTIR experimental parameters used for all resin characterization.

3.1.2. Resin Viscosity: Rheometry

All resin viscosities were determined with a Brookfield CAP 2000+ Viscometer with a 30.25 mm diameter

spindle rotating at 250 RPM. 25.10 μL of resin was dispensed on a frictionless mirror and the spindle was

lowered onto the resin and held for 10 s to equilibrate. The spindle was then rotated for 10 s at a shear

rate of 3,333 s

-1 and viscosities were determined (n = 7). All rheology measurements were done in

accordance with the following industry standards: ASTM D4287, ISO 2884, and BS 3900.

3.2. Light engine characterization

3.2.1. Photomask Optical Density: Atomic Force Microscopy

Atomic force microscopy (AFM, Asylum Research MFP3D) was used to determine the chrome thickness

for all photomasks by using contact mode AFM to image the photopattern topography. A standard force

modulation AFM probe (FM, Nanosensors) was used for all measurements. Photomasks were imaged in

3 arbitrary locations. Image analysis was performed in open source software (Gwyddion). Images were

line flattened along the chrome, then 3-point plane fit to the glass substrate. Resultant height histograms

were then used to determine the mean thickness between glass and chrome (Figure 3). These

measurements were averaged for the 3 locations. From the chrome thickness, modelers can calculate

the optical density of the photomask. Summary of chrome thickness measurements is shown in Table 5.

Figure 3: Contact mode atomic force microscopy topography scan of 300 LPPI Ronchi ruling. Height of

chrome is determined from mean distance between substrate and chrome, determined by histogram.
AMB2022-07 Benchmark Measurements and Challenge Problems – PDF Copy

Table 5: Average thickness of chrome layer in Ronchi ruling photomasks.

3.2.2. Photomask lateral dimensions: Laser Scanning Confocal Microscopy

Laser Scanning Confocal Microscopy (LSCM, Keyence VK2000) was used to determine the lateral

dimensions of the Ronchi rulings. Scans were performed with 20X objective (50X for 500 LPPI features),

auto-brightness adjustment and automatic dual-scan selection. The dual scan function performs a 2nd

LSCM scan at different brightness to enhance sidewall measurement accuracy. Image analysis was

performed in open source software (Gwyddion). Measured line-pairs-per-inch were based on an average

of at least 4 line pairs. Lateral dimensions of masked dmask and un-masked dun-mask regions were measured

from the midpoint of the height step between glass and chrome (Figure 4). Summary of LSCM Ronchi

ruling measurements is shown in Table 6.

Figure 4: Example LSCM measurement on 300 LPPI Ronchi ruling. LPPI was measured across 4 or more

line pairs (7 here). Un-masked feature size dun-maskis measured as indicated and averaged for at least 3

features.
AMB2022-07 Benchmark Measurements and Challenge Problems – PDF Copy

Table 6: Summary of measured Ronchi ruling lateral dimensions

3.2.3. Light engine intensity calibration: Radiometry

Radiometry (Thorlabs, PM100D console, S170C photodiode) was used to determine the optical power of

the 405 LED at the photopatterning plane. The average optical power at the sample plane was 39.3 mW

cm

-2 0.1 mW cm-2 ± (n = 200). As the photopattern exposure time was implemented by turning off and

on the LED source, the LED optical power was also taken as a function of time to allow modelers to

calibrate for any fluctuations in output power (Figure 5). Note: the LED response time was faster than

the radiometer (10 Hz), thus power at the sample plane throughout exposure can be assumed constant.

See Table 7 for all manufacturer-supplied power meter specifications.

Figure 5: Optical power at the photopatterning plane, with triplicate exposures for each exposure time

probed (texp = {1.5, 1.25, 1, 0.9, 0.8, 0.7, 0.6, 0.5} s) to mimic experiment conditions. Violet shaded

regions indicate the duration the LED was on.

Table 7: Optical power meter parameters used for photopatterning plane characterization.

Parameter Value

Sample interval 0.1 s (maximum sampling rate)

Sensor S170C

Type PM100D

Wavelength responsivity 405 nm

3.2.4. Light engine uniformity: Beam Profilometry
AMB2022-07 Benchmark Measurements and Challenge Problems – PDF Copy

The light engine uniformity was calibrated using an optical beam profiler (DataRay, MODEL X). To ensure

sufficient resolution to calibrate the intensity across the photopatterning plane at better resolution than

the smallest photomasks features, a 10X objective (Mitutoyo, M Plano Apo, infinity corrected, f = 200

mm, NA = 0.28) was used with a tube lens (Optem, f = 100 mm) to magnify the projection onto the beam

profilometer sensor (see system design in Figure 1). The beam profilometer + magnification optics

system was then aligned with the photopattern exposure plane and focused using a mechanical linear

micrometer. With the beam profiler aligned to the photopatterning plane, the open-aperture profile of

the light engine was obtained (see Figure 6). For the solution dataset, all beam profilometry images were

taken with each subsequent chrome photomask in the system aligned to the same focal plane.

Note that because the photopattern region was confined using an inset ring-actuated iris, the chrome

photomask could only be placed at a distance approximately 2.5 mm from the aperture, resulting in

defocused edges at the boundaries of the exposure (see Figure 6). Due to this region of defocus at the

pattern edges, a 500 μm by 700 μm subregion at the center, more-uniform region of the photomask was

taken, where the intensity distribution across the subregion and line profile across the entire aperture

are shown in Figure 6(d,b).

To obtain the beam profile measurement, the LED was turned on and the profilometer imaged the

projected pattern, being deliberate to utilize the software absolute-value setting to ensure no

normalization or auto-scaling of the intensity distribution was done. Each intensity distribution was

collected and subsequently exported as a 16-bit tiff file.

Figure 6: (a) Example beam profilometry measurement of the aperture at the photopatterning focal

plane and (b) a representative line profile across the 3 mm aperture. The (c) expanded subsection is the
AMB2022-07 Benchmark Measurements and Challenge Problems – PDF Copy

location where all solution data measurements are taken with (d) the corresponding intensity

distribution.

3.2.5. Light engine spectrum uniformity: Optical Spectroscopy

A spectrum of the nominally 405 nm LED light source (Thorlabs, SOLIS-405C) was collected using a fiber

coupled CCD spectrometer (Avantes, AvaSpec-UL4096CL-EVO). The spectrometer was configured with a

25 um slit and a 600 lines/mm grating that yields a 0.6 nm spectral resolution. Wavelength accuracy was

better than 0.15 nm as confirmed via a Hg/Ar calibration lamp (Avantes, AvaLight-CAL). The instrument

response function was calculated via a NIST traceable halogen light source (Avantes,

AvaLight-HAL-CAL-MINI). The Fresnel reflection from a glass slide was used to direct a portion of the 405

nm LED light source onto a 600 um diameter broadband fiber cable that was connected to the

spectrometer. The data were plotted as “relative irradiance” (i.e. proportional to irradiance –

power/area/bandwidth). The stray light specification given by the manufacturer is 1 % and so features in

the spectrum that are <1 % of the peak relative irradiance are not meaningfully interpretable.

Figure 7: Spectrum of 405 nm LED light source collected from fiber coupled CCD spectrometer.

3.3. Printed feature characterization: Laser Scanning Confocal Microscopy

Laser Scanning Confocal Microscopy (LSCM, Keyence VK2000) was used to determine the lateral

dimensions of the Ronchi rulings. Scans were performed with 20X objective , auto-brightness

adjustment. For basic thickness measurements, single-scan was used, whereas automatic dual-scan was

used for profiles. The dual scan function performs a 2nd LSCM scan at different brightness to enhance

sidewall measurement accuracy. LSCM provides a surface topographic map of the printed line features

with excellent X, Y and Z resolution.

3.3.1. Cure depth measurement, cure profiles, working curve
AMB2022-07 Benchmark Measurements and Challenge Problems – PDF Copy

The cure depths were measured by 3-point plane fitting the LSCM data to the coverglass substrate, then

measuring the maximum height on 20 separate profiles along the feature’s length (Figure 8). The 20

maximum height values were averaged to obtain a mean maximum height. These mean maximum height

measurements were repeated for 3 replicate prints. Working curve measurements utilized the P1 pattern

prints (25 LPPI) with an expanded range of exposure duration (from 0.5 s to 1.5 s) (Figure 9). With the

500 μm photomask, the resultant prints are considered large enough to be bulk-like in their cure.

Figure 8: (a) Laser scanning confocal microscopy of an exemplary 25 LPPI feature (resin 4, 0.7 s exposure)

indicating 20 line profiles over which average cure depth was measured. Dark regions are feature

sidewalls, which were not captured in this scan. (b) Height map of exemplary feature. (c) Also shown is a

profile of the feature, which should be predicted for the smaller features in (CHAL-AMB2022-07-03). The

solution profiles will be averaged over at least 3 prints to establish mean value and uncertainty.

The measured working curve is provided here for convenience. Data are plotted as cure depth vs

exposure on Linear-Log scale.
AMB2022-07 Benchmark Measurements and Challenge Problems – PDF Copy

Figure 9: Measured working curve (cure depth vs exposure) for the 4 resins with 25 LPPI photomask,

obtained from LSCM.

Table 8: Working curve raw data.

4. Description of Benchmark Challenge Problems
AMB2022-07 Benchmark Measurements and Challenge Problems – PDF Copy

4.1. CHAL-AMB2022-07-OP

The optical profile challenge asks the modelers to predict, at the print plane, the intensity profile

(intensity in mW cm

-2 versus lateral position) of the photopattern for each of the seven photomasks. The

modelers may choose to use this best prediction in their cure predictions, or they may simplify the

prediction as they see fit. The measured optical profiles cannot accurately capture the expected high

contrast of the chrome photomask, thus verification will be restricted to the maximum intensity and full

width half max (FWHM). The solution score for this challenge problem will be based on total RMS error

between predicted and measured maximum intensity and FWHM.

4.2. CHAL-AMB2022-07-CD

The cure depth challenge asks the modelers to predict the cure depth, as measured by LSCM at the

center of the feature, as a function of photomask linewidth, exposure duration, and resin type. The

resins exhibit varying degrees of reactivity and viscosity, and thus the interplay between reaction and

species diffusion can be expected to differ in the different resins, which may affect cure depth.

Solutions shall be judged on both a relative and absolute basis.

The resin dependent relative solution will account for 30 % of the score and will be determined by the

minimum RMS error in determining the cure depth ratios between the 4 resins at 0.5 s exposure

duration for the 200 LPPI mask.

The pattern size dependent relative solution will account for 30 % of the score and will be determined

by the minimum RMS error in determining the cure depth ratios for resin 2 (low viscosity, low reactivity)

resins at 0.5 s exposure duration for each of the masks.

The absolute solution, worth the additional 40 % of the score, will consider the total RMS error between

modeled cure depth and measured cure depth for all 4 resins, all 4 exposure durations and 6

photomasks (from 50 LPPI to 300 LPPI).

4.3. CHAL-AMB2022-07-PP

The print profile challenge asks the modelers to predict the cross-sectional profile (i.e. thickness versus

lateral position) of the printed features for each of the 4 resins, 4 exposure durations and 6 photomasks

(from 50 LPPI to 300 LPPI).

The solutions will be evaluated on a per resin basis, with each resin worth 25 % of the total score, and

each evaluated as the total RMS error between the modeled and measured profiles.

5. Description and Links to Associated Data

All data available to support the AMB2022-07 challenges are contained in the “Resin properties, light

engine calibration, and calibration print dimensions (AMB2022-07)” dataset available here:

https://doi.org/10.18434/mds2-2597 .

New data files, updates, and/or changes to download URLs may be made periodically. Users should refer

to the README text file which will record all updates. Additionally, the NIST Public Data Repository (PDR)

undergoes frequent updates. If file downloads fail or are unavailable, users should wait several hours

before contacting the technical support listed on the AMB2022-07 dataset webpage.

5.1 File Naming Convention
AMB2022-07 Benchmark Measurements and Challenge Problems – PDF Copy

All measurement data files followed a similar naming convention to the specimen naming convention.

For the master compressed file names found in the data repository, the names have been consolidated

for clarity. A description of the naming conventions is found below, with specific examples pertaining to

each dataset listed in subsection format. We note that for all measurements where a portion of the

designated filename structure is not used (e.g., not all experiments required resin), ‘none’ has been used

in its place (as will be demonstrated below).

Master compressed file naming convention:

AMB2022-07_{measurement}_Challenge.zip

AMB2022-07_{measurement}_Solution.zip

Measurement file naming convention:

AMB2022-07_{measurement}_{experiment date}_{resin used}-{ν}{k}_{Ronchi ruling used}_{exposure

time}_{specimen slide number}_{row number}_{column number}_{replicate}

5.1.1. Fourier Transform Infrared Spectroscopy

Measurement name: FTIRVP

Master compressed file names:

AMB2022-07_FTIRVP_Challenge.zip

AMB2022-07_FTIRVP_Solution.zip

Measurement file name example for an FTIR experiment done on April 18th, 2022 using Resin 1 (high

viscosity, low reactivity) and is the first replicate:

AMB2022-07_FTIRVP_2022-04-18_Re1-HL_none_none_none_none_none_n1

5.1.2. Rheometry

Measurement name: RheoVP

Master compressed file names:

AMB2022-07_RheoVP_Challenge.zip

AMB2022-07_RheoVP_Solution.zip

Measurement file name example for a rheometry experiment done on April 18th, 2022 using Resin 1

(high viscosity, low reactivity) and is the first replicate:

AMB2022-07_RheoVP_2022-04-18_Re1-HL_none_none_none_none_none_n1

5.1.3. Atomic Force Microscopy
AMB2022-07 Benchmark Measurements and Challenge Problems – PDF Copy

Measurement name: AFMVP

Master compressed file names:

AMB2022-07_AFMVP_Challenge.zip

AMB2022-07_AFMVP_Solution.zip

Measurement file name example for an AFM experiment done on April 18th, 2022 using a 25 LPPI Ronchi

ruling and is the first replicate:

AMB2022-07_AFMVP_2022-04-18_none_25LPPI_none_none_none_none_n1

5.1.4. Laser Scanning Confocal Microscopy

Measurement name: LSCMVP

Master compressed file names:

AMB2022-07_LSCMVP_Challenge.zip

AMB2022-07_LSCMVP_Solution.zip

Measurement file name example for a cure depth LSCM experiment done on April 18th, 2022 using

Resin 1 (high viscosity, low reactivity), a 25 LPPI Ronchi ruling, a 0.6 s exposure time, is slide number 3, is

located in row 2, column 3, and is the first replicate:

AMB2022-07_LSCMVP_2022-04-18_Re1-HL_25LPPI_0600ms_3_r2_c3_n1

Measurement file name example for a photomask dimension LSCM experiment done on April 18th, 2022

using a 25 LPPI Ronchi ruling and is the first replicate:

AMB2022-07_LSCMVP_2022-04-18_none_25LPPI_none_none_none_none_n1

5.1.5. Radiometry

Measurement name: RadVP

Master compressed file names:

AMB2022-07_RadVP_Challenge.zip

AMB2022-07_RadVP_Solution.zip

Measurement file name example for a radiometry experiment done on April 18th, 2022 using an open

aperture and is the first replicate:

AMB2022-07_RadVP_2022-04-18_none_none_none_none_none_none_n1

5.1.6. Beam Profilometry

Measurement name: BeamVP

Master compressed file names::
AMB2022-07 Benchmark Measurements and Challenge Problems – PDF Copy

AMB2022-07_BeamVP_Challenge.zip

AMB2022-07_BeamVP_Solution.zip

Measurement file name example for a beam profilometry experiment done on April 18th, 2022 using an

open aperture and is the first replicate:

AMB2022-07_BeamVP_2022-04-18_none_none_none_none_none_none_n1

Measurement file name example for a beam profilometry experiment done on April 18th, 2022 using a

25 LPPI Ronchi ruling and is the first replicate:

AMB2022-07_BeamVP_2022-04-18_none_25LPPI_none_none_none_none_n1

5.1.7. Optical Spectroscopy

Measurement name: OptSpecVP

Master compressed file names:

AMB2022-07_OptSpecVP_Challenge.zip

AMB2022-07_OptSpecVP_Solution.zip

Measurement file name example for a optical spectroscopy experiment done on April 18th, 2022 and is

the first replicate:

AMB2022-07_OptSpecVP_2022-04-18_none_none_none_none_none_none_n1

5.8. Digital Caliper (slide thickness)

Measurement name: CaliperVP

Master compressed file names:

AMB2022-07_CaliperVP_Challenge.zip

AMB2022-07_CaliperVP_Solution.zip

Measurement file name example for a slide thickness experiment done on April 18th, 2022, is slide

number 3, and is the first replicate:

AMB2022-07_CaliperVP_2022-04-18_none_none_none_3_none_none_n1

6. References

N/A

7. Disclaimer

The National Institute of Standards and Technology (NIST) uses its best efforts to deliver high-quality

copies of the AM Bench database and to verify that the data contained therein have been selected on
AMB2022-07 Benchmark Measurements and Challenge Problems – PDF Copy

the basis of sound scientific judgment. However, NIST makes no warranties to that effect, and NIST shall

not be liable for any damage that may result from errors or omissions in the AM Bench databases.

Certain commercial equipment, instruments, or materials are identified in this paper in order to specify

the experimental procedure adequately. Such identification is not intended to imply recommendation or

endorsement by NIST, nor is it intended to imply that the materials or equipment identified are

necessarily the best available for the purpose.