29.1: A Real‐time On‐line Illumination and Light Decline Monitoring Technology
Authors: Wang Fu Guo 
Published: August 2023

Mask plays major role in the photolithography process during
whole TFT manufacturing. The photolithography process
transfers the desired pattern on mask into panel substrate, which
forms some portions of device and performs some electric or
optical functions. Due to pattern continuously duplicated, a
correct pattern shape of mask is very important in the
photolithography process. An abnormal pattern will results in
huge loss of yield and cost.

The haze, a foreign matter grown or deposited on the surface of
mask, is already a prevalent phenomenon in TFT
photolithography manufacturing or well known in
semiconductor manufacturing. It is already well identified that it
is highly related to the storage environment of mask, that is, the
so called AMC (Airborne Molecular Contamination).

A summarized mask haze classification based on past industrial
service experience is proposed and a case study result with haze
sampling at the site of mask manufacturer is followed in this
review to show the understanding of the recently state of the art
about mask haze in TFT industry.

With the development of industrial technology, the clean room
area of TFT panel and semiconductor plant construction project
is getting larger and larger (a single clean area of 100,000
square meters), and the investment cost is getting higher and
higher. The owners have higher and higher requirements on the
cost control and intelligence of the project, including plant
construction cost, operating cost and energy saving, which have
been highly concerned by the owners. In the actual execution of
TFT panels and semiconductor projects, owners often hear the
problems about clean room lighting system, which are
summarized as follows:

The illumination required by the process is 400lux, and the
initial design is 600lux. By artificially opening the number of
lamps, the attenuation problem of the light source for a long
time in the later period is compensated. The owner needs to close
several circuits of lamps in the early stage to meet the
illuminance requirements of the clean room. If the lamps and
lanterns are not closed in the early stage, part of the operation
cost and energy waste will be caused;

With the passage of time, the illumination of clean room will
also decrease with time, and when to what illumination should
be opened several circuit lamps, in order to meet the needs of
clean room process? But also not waste energy and so on;

With the operation of the plant, when can the illumination of
the clean room lamps and lanterns not meet the requirements of
the process when they are all opened? And when do light
fixtures need to be replaced?

Part of the lamps are broken. Whether the illuminance of the
clean room in this area is much lux, and whether it meets the
illuminance demand of the process, etc.;

In the illuminance test when the project is completed and
handed over to the owner, it is usually done by outsourcing or
management personnel at different points to measure manually
on the spot, which consumes time and labor cost, and if the instrument measurement is wrong, the amount of newly
measured works is relatively huge, etc.

When do clean room lamps need to be replaced?

The owner will normally deal with the above problems:

If more experienced owners turn on or off the number of
lamps and lanterns based on their experience, there are also
risks of energy waste and insufficient illumination;

All open to meet the illuminance demand, there is excessive
waste of energy and operation costs;

With the passage of time, light source attenuation, part of the
lamps are broken, usually artificial field measurement, to
confirm whether the lamps need to be replaced, time and labor
costs;

If the process department doubts the illuminance value of the
factory department, it also needs to measure on site or find the
data of the completed illuminance test before as the basis,
especially the existing clean room renovation project;

The measurement of completion acceptance is usually on‐site
measurement or outsourcing can provide corresponding data to
prove acceptance, etc.;

According to the above problems, this paper describes a real‐
time online illuminance and light decline monitoring technology
to deal with the actual problems of TFT panel and
semiconductor.

Automatic control is realized for the closing and opening of
the owner's lamps through the cumulative average illuminance,
etc., and the requirements of the process illuminance are met to
save energy consumption and operating costs;

The real‐time cumulative monitoring of the luminescence life
curve of this technology is compared with the luminescence life
curve provided or tested by the manufacturer, which can
confirm the early warning and comparison of the deviation
between the actual luminescence life and the luminescence life
provided by the manufacturer, so that the owners can purchase
or replace the number and area of the luminescence in advance;