Japan Analytical Industry Co., Ltd.
Naoki Oguri Ph. D.
VOC analysis in the Cleanroom
1. Sampling Method
Sampling tool for volatile organic compounds (VOC) is shown in Fig. 1.

Model Al-410

Model Al-430

Fig. 1 Photos of air samplers

Both air samplers are designed to collect gas in environmentalor cleanroom air into a primary adsorption tube (PAT) by suction.
The samplers can be operated by internal battery. The samplers
have the same capability. However, model AL-430 includes aflow calculator.
The samplers can be sucked air with 1,000 ml/min of flow ratein order to samlple a large amount of the air in the cleanroom,
because diameter of the primary adsorption tube (PAT) for Purge& Trap sampler model JHS-100A has excess wide bore
(i.d. 12 mm) against to the other company's tubes.
Normally, 40-50 mg at the most of adsorbent are packed into
the other company's tube. However, illustrated adsorbent on
Fig. 2 was packed in the PAT.
In order to evaluate the VOC in the cleanroom, a larger sampling
volume is needed. According from our experience, JAI recommends
total of 10,000 ml (1,000 ml for 10 to 20 min) of the air for VOC
analysis in the cleanroom .
Fig. 2 Primary adsorption tube

The PAT widely conduce applications for VOC analysis from Hard Disk, wafer, liquid crystal display and otherelectronic devices. i.e. after VOC collection by a PAT, the PAT with PAT holder then transferred to purge &trap sampler JHS-100A and GC/GS. So that VOC characterizaljon can be performed.

2. VOC Analysis of LCD Manufacturing Processes

Figure 3 shows the chromatograms of VOC obtained fromthe 5 manufacturing processes in the LCD industry.
Total VOC amounts in the chromatograms are summed
up as the total ion currents. ( 15 ,120 )The chromatogram obtained from rubbing room was alsosimilar to that of the coating room. However, from both total
VOC amounts, 14 % of exhaust gas from coating room
entered into the rubbing room by circulation.
(Total VOC amount : 2,130)

By the way, the sealing & printing room is located next tothe coating room, but, cellosolves and NMR peaks fromthe coating room airs are not observed in the chromatogramsof the sealing and printing room.(Total VOC anrount : 2,066)
The acetone and IPA detected in the sealing & printing room
came from the rubbing room.

In the fourth chromatogram from the top, absence of VOC in
the blending room indicates an ideal cleanroom condition.
(Total VOC amount : 42)

At the degassing room, Iiquid crystai injected into the display
is heated in order to remove bubbles in the liquid.
The chromatogram of the degassing room air shows similar
chromatogram as of rubbing room. However, we could not
determine it the VOC came from the rubbing room or from theexhaust from the liquid crystal.
Also, the total VOC amount was calculated to be 1,137.

Figure 3 The chromatograms of VOCs
obtained from the 5 manufacturing
process is in the same LCD industry

3. Modification of ventilation order in the cleanroom

ldeal cleanroom condition at the blending room is shown in the fourth chromatogram from the top of Fig. 3.
However, the ideal chromatogram was obtained after the modification of ventilation order in the cleanroom
with changing the flow rate and the passthrough order in the cleanroom.
Before and after chromatogram were shown in Fig. 4.
The before chromatogram (the top) was obtained. Butyl cellosolve acetone, IPA, NMP and iso-propyl
acetate were observed. The total VOC amount for was 606.

The after modification chromatogram was same as Fig. 3, on this case, the total VOC amount was only 42 .

Figure 4 VOC chromatograms of before and after modificationof ventilation at the blending room in the clcanroom

As a result, it is clearly that the ideal VOC condition for the bending room was obtained by measurement of
VOC by using the air sampler and P&T-GC/MS.