HIRANUMA APPLICATION DATA

Automatic Titrator

Data No.

F9Apr. 5,
2019

Determination of alkaline component
in photoresist remover solution

Electric &Electronics
1. Abstract

Strong alkaline solution is used as remover for residual photoresist on the substrate after the developmentof the substrate for liquid crystal display instrument etc. The composition depends on the intended use but
sodium hydroxide, potassium hydroxide, and tetramethylammonium hydroxide (TMAH) are used as remover.
TMAH can be determined by potentiometric titration with hydrochloric acid standard solution. TMAH
could absorb carbon dioxide gas and generate carbonates, it indicates another inflection point at pH around 4
on the titration with hydrochloric acid standard solution. This report introduces an example of fractional
determination for TMAH and carbonates.

N(CH3)4OH ＋ HCl[N(CH3)4]2CO3 ＋ HCl→ N(CH3)4Cl ＋ H2O→ N(CH3)4HCO3 ＋ N(CH3)4Cl･･･(1)･･･(2)The reactions between TMAH and hydrochloric acid is described in formula (1), carbonate andhydrochloric acid is shown in formula (2). Carbonate generates hydrogen carbonate on reaction (2), it iscontinuously titrated with hydrochloric acid to the endpoint at around pH 4. The reaction between hydrogencarbonate salt and hydrochloric acid is indicated in formula (3).

N(CH3)4HCO3 ＋ HCl→

N(CH3)4Cl ＋ CO2 ＋ H2O･･･(3)2. Configuration of instruments and reagents(1) Configuration of instruments
Main unit:

Hiranuma Automatic Titrator COM series

Electrodes:

Glass electrodeGE-101B

Reference electrodeRE-201Z*The following electrodes are usable instead of the above electrodes.
・Glass reference combination electrode GR-501BZ…Fixed sleeve type・Glass reference combination electrode GR-511BZ…Moveable sleeve type(2) Reagents
Titrant: 0.5 mol/L Hydrochloric acid standard solution

3. Measurement procedure(1) Take about 25 g of sample into a 50 mL beaker and weigh accurately.
(2) Immerse electrodes and start titration with 0.5 mol/L hydrochloric acid standard solution.

4. Measurement conditions and results
Examples of titration conditions(1) Titration of TMAH and carbonates
Cndt No.
MethodBuret No.
Amp No.
D. Unit
S-Timer
C.P. mLT Timer
D.P. mLEnd Sens
Over mL
Max.Vol.

1Auto

1
1pH
5
11.5503000020sec
mLsec
mL
mLmL

ConstantNo.
SizeBlank
Molarity
FactorKL
Unit
FormulaDecimal Places
Auto In Pram.

125.1398 g0 mL
0.5 mol/L
1.005
91.15
0%

Mode No.
Pre Int
Del K
Del Sens
Int Time
Int Sens
Brt Speed
Pulse

2209023220Mode No.
Pre Int
Del K
Del Sens
Int Time
Int Sens
Brt Speed
Pulse

2300023220sec
mV
sec
mV

(VA-VB)*F*M*K/(S*10)
4Non(2) Titration of hydrogen carbonate salt
Cndt No.
MethodBuret No.
Amp No.
D. UnitS-Timer
C.P. mLT Timer
D.P. mLEnd Sens
Over mL
Max.Vol.

2
Auto

1
1
pH
00005000
0.1
20

sec
mL
sec
mL
mL
mL

ConstantNo.
SizeBlank
Molarity
FactorKL
Unit
FormulaDecimal Places
Auto In Pram.

2
25.1398
00.5
1.005
208.3
0%

g
mL
mol/L

(D-B)*K*F*M/(S*10)
4NonsecmV
secmVMeasurement results
Measurement results of TMAH
Number ofMeasurement

Size(g)Titrant
Volume (mL)Concentration
(%)

123

25.1153
25.1280
25.1398

12.83612.83712.8392.28642.28472.2827Avg.
SDRSD

Statistic
calculation

2.285 %
0.0019 %0.08 %

Measurement results of carbonates<Expanded figure>

Number ofMeasurement
123Size(g)25.1153
25.1280
25.1398

Statistic
calculation

Titrant
Volume (mL)
0.299
0.303
0.310

Avg.
SD
RSD

Concentration(%)
0.12460.12620.12910.127 %
0.0023 %1.80 %

Example of titration curve

5. Note(1) Measurement method
TMAH is strong alkaline reagent which absorbs carbon dioxide gas in the air and generates carbonates.
Purging air on sample solution with nitrogen gas can reduce the influence of carbon dioxide on the titration.
Using air passed through soda lime absorption column instead of nitrogen gas also has a positive effect.
Water wasn't added to sample; non-diluted sample was titrated directly in this measurement. Please pay
attention to carbonic acid in the water when it is added for the sample dilution before the titration.
(2) Sample measurement with little carbonates content
The obvious inflection point come from carbonates (second inflection point) was obtained at the endpoint inthis report because the sample contained the certain amount of carbonate. Therefore the endpoint detection
method was set to “Auto” which detects inflection point automatically. It sometimes shows the unclear
inflection point when the sample contains little carbonates. In that case, set the endpoint detection method
for carbonate to “Set” with “pH 4” as endpoint. The sodium carbonate was directly titrated with thehydrochloric acid standard solution in this report. There is another method to titrate the barium carbonate
generated by the addition of barium chloride in advance. This method is useful for a sample containing lessamount of sodium carbonate. The inflection point for the carbonate becomes single on the titration curve.
(The first inflection point is come from only TMAH, and the second inflection point is come from only
sodium carbonate (barium carbonate).) This method is useful to determine the low carbonate concentration
because the titrant volume to determine the carbonate concentration gets twice.
(Please refer to application note F10 regarding barium chloride addition method.)
Keywords: Tetramethylammonium hydroxide, TMAH, Remover, Carbonates, Neutralization titration*Some measurement would not be possible depending on optional configuration of system.