Application Note
Semiconductor

Analysis of Nanoparticles in Organic
Reagents by Agilent 8900 ICP-QQQ
in spICP-MS ModeDetermination of 25 and 30 nm Fe3O4 NPs
in low-particle concentration solutionsAuthor
Donna Hsu, Yoshinori
Shimamura, Brian Liao,and Michiko Yamanaka1
Chun-Hua Chen andChiu-Hun Su2
Ching Heng Hsu3
1

Agilent Technologies, Inc.

Industrial Technology ResearchInstitute of Taiwan, Taiwan
23

BASF Taiwan Ltd., Taiwan

Introduction
Semiconductor device manufacturing involves several processes including
lithography, etching, ion implantation, and peeling. Even small amounts of impurities
present in processing reagents such as developer, rinse solution, and etching liquid
can cause defects, resulting in a reduction of product yield and degradation ofproduct reliability. Metallic nanoparticles (NPs), especially iron (Fe) NPs, can lead tothe occurrence of ‘cone defects’ on the surface of wafers, which cause shorting ofelectrical signals (1). To prevent these problems from arising, an accurate analyticalmethod is required to determine metallic NPs in semiconductor process chemicals.
Single particle ICP-MS (spICP-MS) is a powerful tool that is used increasingly tocharacterize the NP content of various types of samples (2–4). spICP-MS allows
the simultaneous determination of the number, concentration, and size of particles,
plus the dissolved element concentration. It can be applied to the measurement ofsemiconductor grade organic solvents such as isopropyl alcohol (IPA), propylene

glycol methyl ether acetate (PGMEA), and butyl acetate(BuAc), as well as aqueous solutions (3). To detect verysmall-sized NPs using spICP-MS, an instrument with a low
background and high sensitivity such as the Agilent 8900
Triple Quadrupole ICP-MS (ICP-QQQ) is needed. Also, sincesome metallic NPs suffer from spectral interferences, theadvanced interference removal capability of the 8900
ICP-QQQ is advantageous for the application.
In this study, Fe NPs were measured in semiconductor grade
IPA, PGMEA, and BuAc using the Agilent 8900 ICP-QQQ
operating in spICP-MS mode.

Experimental
Sample preparation
Two kinds of Fe3O4 NP (Fe NP) solutions, 25 nm (SigmaAldrich, p/n 900027) and 30 nm (Sigma Aldrich, p/n 747408),
were used as NP standards. The Fe NPs were spiked into IPA,PGMEA, and BuAc. These organic solvents were introduced
directly to the ICP-QQQ. To measure the ionic sensitivity of Fe,
an aqueous Fe standard (1000 ppm, Kanto Chemicals, Japan)
was diluted with each organic solvent.

between measurements. Data analysis was performed using
the Single Nanoparticle Application Module of the Agilent
ICP-MS MassHunter software.
The operating conditions of the Agilent 8900 ICP-QQQ
are detailed in Table 1. As shown, slightly different
parameters were used to achieve optimum sensitivity for thedetermination of Fe NPs in each solvent. To enable the direct
injection of organic solvents to the ICP-QQQ without
the deposition of carbon on the cones, oxygen gas (20%,Ar balanced) was added to the sample gas flow.
Table 1. ICP-QQQ operating conditions.
Parameter

RF power (W)ValueIPA

PGMEA

BuAc

1400

1500

1500

Sampling depth (mm)18.0

Nebulizer gas (L/min)

0.70

Makeup gas (L/min)

0.50

0.60

0.45

*Option gas (L/min)

0.40 (40%)

0.20 (20%)

0.40 (40%)

Spray chamber temp. (°C)

2

Instrumentation

Extraction lens 1 (V)–150–125–125

An Agilent 8900 ICP-QQQ (#200, Semiconductor
configuration) and Agilent SPS 4 autosampler were used
for all measurements. The sample introduction systemcomprised a quartz torch with a 1.5 mm i.d. injector, quartz
spray chamber, and platinum-tipped interface cones. TheSPS 4 autosampler was fitted with a sample rack (producedin Taiwan) designed to accommodate larger sample bottles(100 to 500 mL). Being able to load the same bottles used
for sample preparation into the SPS 4 rack reduces the riskof contamination as the samples don’t need to be transferred
to smaller bottles. Also, larger bottles are convenient for thelong-term stability test. The samples were self-aspirated using
an Agilent PFA nebulizer, which is part of the SPS 4 probe
kit (p/n G3139-68000). Clean argon gas was purged into thecover of the autosampler and there was a constant flowof ultrapure water via a continuous flow rinse port fitted tothe SPS 4.

Extraction lens 2 (V)

–10

–15

–15

Octopole bias (V)

–10

–3–3

The 8900 ICP-QQQ was operated in MS/MS mode for all Fe
measurements. Both Q1 and Q2 (unit mass filters) were set tom/z 56. Q1 selects which elements enter the ORS4 collision/reaction cell (CRC), allowing controlled reaction chemistry totake place in the cell when a reactive cell gas is introduced.
Ammonia cell gas was used to control the ArO and C2O2
interferences that overlap Fe at m/z 56.
The signal generated by a single NP lasts for about 1 ms,
so Fast Time Resolved Analysis (TRA) mode of the 8900
ICP-QQQ was used to acquire the data. Fast TRA allows single
element acquisition at a sampling rate of 100 μs (10,000measurements per second) and no settling time is needed

2Axial acceleration (V)Energy discrimination (V)

1.5–10He flow rate (mL/min)**NH3 flow rate (mL/min)–7–7

12 (20%)Dwell time (μs)
Masses monitored
Data acquisition time (s)3 (30%)

3 (30%)

100Fe (Q1: 56, Q2: 56)
60*20% O2 balanced with Ar added using the option gas mass flow controller, which is fitted as
standard on the Agilent 8900 Semiconductor ICP-QQQ. **10% NH3 balanced with He.

Results and discussion
Analysis of Fe NPs in IPA, PGMEA, and BuAc
Solutions of IPA, PGMEA, and BuAc containing 30 nm FeNPs spiked at 5 ppt were measured using the 8900 ICP-QQQ.
The signal distribution and size distribution plots for Fe NPs
in each of the samples are shown in Figure 1. The signals
generated from the Fe NPs were clearly separated from thebackground signals. Also, the mean measured particle size
was around 30 nm in all spiked solvents, which is consistent
with the nominal Fe NP diameter (30 nm). The SingleNanoparticle Application Module software automatically sets
the particle threshold, which is shown by the pink line in thesignal distribution plots.

1PGMEA

Signal (CPS)

Particle size (nm)Signal (CPS)

Normalized frequency

Normalized frequency

Signal (CPS)

Normalized frequency

BuAc
Frequency

Frequency

Frequency

IPA

Particle size (nm)Particle size (nm)The spICP-MS software automatically calculates thenebulization efficiency, which is the ratio of the amountof analyte entering the plasma to the amount of analytedelivered to the nebulizer. By measuring 30 nm Fe NP, thenebulization efficiency (calculated by size) was found tobe around 0.30 (30%) for all three organic solvents. The
sensitivity of ionic Fe ranged from 1500 cps/ppt to 2400 cps/ppt depending on the solvent. The background equivalentconcentration (BED) of the blank reagents was around 6 nm.

Linearity of detected particle number concentrationin terms of spiked concentration
Figure 2 shows the size distribution of 25 nm Fe NPs
dispersed in IPA solution at several concentrations (0, 0.1,0.5, 1, and 2 ppt). The graph clearly indicates a Gaussian
distribution for 0.5, 1, and 2 ppt of Fe NPs. It wasn’t possible
to detect NPs smaller than 18 nm due to the backgroundsignal from the small amount of ionic Fe present in thesample (BEC = 0.6 ppt).

Particle concentration (particles/L)

Figure 1. Signal distribution (upper) and size distribution (lower) of 30 nm Fe
NPs in2 solutions of IPA, PGMEA, and BuAc.
FigureParticle size (nm)Figure 2. Size distribution data for 25 nm Fe NPs spiked at 0, 0.1, 0.5, 1, and2 ppt in IPA. The vertical axis shows the particle number concentration foreach range of particle sizes (each bar represents a size range of 2 nm).

3

Figure 3 shows the relationship of measured particle numberconcentration (particle/L) against the spiked concentrationof Fe NPs in IPA. Almost perfect linearity (R2 = 0.998) was
obtained across the concentration range of 0.1 to 2 ppt.
These results show that 25 nm Fe NPs can be determined in
IPA solutions containing very low concentrations of Fe NPs
using the 8900 ICP-QQQ operating in spICP-MS mode.

Long-term stability test
Figure 4 shows the stability of detected particle number(representing particle number concentration) and particle sizefor 30 nm Fe NPs in the three solvents over 12 hours. Boththe detected particle number and the size were constant over
12 hours, as indicated by the %RSDs. The stability of Fe NPs
in each solvent means they can be measured accurately,even a long time after sample preparation.

Measured particle concentration (particles/L)

Conclusion
R2=0.998

Using an spICP-MS method, the Agilent 8900 ICP-QQQ
operating in MS/MS mode was used for the determinationand characterization of iron-based nanoparticles in IPA,PGMEA, and BuAc.
Standards containing 25 or 30 nm Fe3O4 nanoparticles
were spiked into the organic solvents and the particle size
and the particle number concentration were determinedusing the spICP-MS method. The small-sized particles
were successfully measured in solutions with a particle
concentration ranging from 0.1 to 2 ppt. Also, the particle sizeand particle concentration of Fe NPs were stable in each of
the three organic solvents over 12 hours.

Figure 4
Spiked concentration (ppt)

Overall, the method delivered the low background, sensitivity,and spectral interference removal necessary for the analysis
of small-sized NPs in semiconductor grade organic solvents.

Particle size (nm)Detected particle number (particles/min)Figure 3. Relationship between the spiked concentration of 25 nm Fe NPs
and measured particle number concentration in IPA.

Time (hour)Time (hour)

Figure 4. Long-term stability of 30 nm Fe NPs in IPA, PGMEA, and BuAc over 12 hours. The left graph shows the detected particle number and the right graph shows
the average particle size. The numbers in parentheses are RSD%.

4

References
1.

Takuya Hagiwara, Kentaro Saito, Hiraku Chakihara,Shuji Matsuo, Masao Inoue, Seiji Muranaka, Yuki Ota,
Masazumi Matsuura, Study on Cone-defects during
the Pattern Fabrication Process with Silicon Nitride,
J. Photopolym. Sci. Technol., 28, No.1, 2015, 17–24

2.

Michiko Yamanaka and Steve Wilbur, Measuring Multiple
Elements in Nanoparticle using spICP-MS: Acquire
NP data for up to 16 elements in Rapid Multi-Element
Nanoparticle Analysis Mode, Agilent publication,5994-0310EN

3.

Yoshinori Shimamura, Donna Hsu, and MichikoYamanaka, Multielement Nanoparticle Analysis ofSemiconductor Process Chemicals Using spICP-QQQ:
Characterization of Ag, Fe3O4, Al2O3, Au, and SiO2 NPs
in TMAH in a single analytical run, Agilent publication,
5994-0987EN

4.

Michiko Yamanaka and Steve Wilbur, Accurate
Determination of TiO2 Nanoparticles in Complex
Matrices using the Agilent 8900 ICP-QQQ, Agilent
publication, 5991-8358EN

www.agilent.com/chem

This information is subject to change without notice.
© Agilent Technologies, Inc. 2019
Printed in the USA, August 28, 20195994-1306EN