Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
2000-11-10
2001-09-18
Lefkowitz, Edward (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S605000, C340S608000, C340S618000, C073S053010, C118S712000, C239S071000
Reexamination Certificate
active
06292103
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Taiwan application serial no. 89214122, Aug. 15, 2000.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a waste liquid discharge system. More specifically, the present invention relates to a blockage alarm system for a waste liquid discharge machine which enables operators to have early knowledge of a blockage and thus have sufficient time to handle the situation.
2. Description of the Related Art
Photolithography is an important process for semiconductor fabrication. Every part of a semiconductor device such as patterns in the layers and regions implanted with dopants are formed using photolithography. Therefore, the number of lithography processes to be performed or the amount of masks required is a reflection of how difficult a fabrication process is.
Although the photolithography is complex, the basic principle thereof is simple. First, a layer of photosensitive material is applied on a surface of a die. The layer is radiated with parallel light from a light source through a mask mainly made of glass. The pattern on the mask is projected onto a surface of a die and selective development is performed, by which the pattern is transferred to the die. The photosensitive material on the surface of the die is called as a photoresist.
Currently, almost all of the photoresists are coated on the die by spin coating to obtain a photoresist having uniform thickness, high adhesion and no defects. Referring to
FIG. 1
, a schematic, cross-sectional view of rotator for spin coating and a conventional waste liquid discharge system are shown. The shift of the rotator
10
provides an appropriate vacuum to attach the wafer
12
thereon. When the rotator
10
rotates the wafer
12
, the photoresist liquid
14
applied on the surface of the wafer
12
is moved toward the edge of the wafer
12
due to the action of the centrifugal force and finally a photoresist layer
16
having a uniform thickness is formed.
With high speed rotation of the rotator, some photoresist liquid
21
is spun off the wafer
12
. Usually, a fixed container
20
is used to surround the wafer
12
to collect photoresist liquid spun off of the wafer
12
, as shown in FIG.
1
. The photoresist liquid
21
is transported to a discharge line
26
through the sides
22
,
24
of the fixed container
20
. Because the photoresist liquid is a liquid with high consistency, blockage often occurs in the non-vertical sections such as transversal transmitting part
28
in
FIG. 1
when the discharge line
26
is not arranged in vertical direction. The photoresist may accumulate up to a level higher than the height of the machine and flow back on the machine. It is dangerous for the machine and operators because the above waste liquid may be a toxic waste liquid. If the toxic liquid is spilled, it takes time to evacuate people from the scene and perform post treatment.
SUMMARY OF INVENTION
Therefore, it is one object of the present invention to provide an alarm system for detecting waste liquid discharge blockage, which provides early warning when blockage occurs in the above discharge lines to inform operators of the situation and enable them to have enough time to handle the same.
The present invention provides an alarm system for detecting waste liquid discharge blockage which provides previous warning when blocking results from waste liquid generated in a plurality of machines. The above alarm system for detecting waste liquid discharge blockage comprises a discharge line, a sensing line, at least one sensor and an alarm.
The discharge line is connected to a plurality of outlets of the machine to receive waste liquid discharged, in which a section of the discharge line under the connection of the discharge line and the lowest outlet is selected as a sensing region. The discharge line of the sensing region is angled with respect to the horizontal in the range of 185 to 265 degrees so the waste liquid can flow smoothly. The sensing line has a first pipe and a second pipe, both arranged in the sensing region. The angle between the first pipe and the discharge line of the sensing region is in the range of 95 to 175 degrees when the discharge line of the sensing region is vertical. The angle between the second pipe and the discharge line of the sensing region is in the range of 95 to 175 degrees when the discharge line of the sensing region is vertical. Further, at least a sensor is located in the sensing line, which sensor outputs a sensor signal when detecting any waste liquid.
With the design of the sensing region of the discharge line angled in the range of 185 to 265 degrees with respect to the horizontal, the waste liquid can be discharged smoothly. Even when blockage occurs, the improper flow of waste liquid into the sensing region, which would affect the detection of waste liquid blockage inside the sensor, can be inhibited by the arrangement of the first pipe and the second pipe in the sensing region and control of the angle in the range of 95 to 175 degrees when the discharge line of the sensing region is vertical.
The above waste liquid can be photoresist liquid, for example. The angle between the first pipe and the discharge line and the angle between the second pipe and the discharge line can be designed to be the same. The alarm can be a beeper, a speaker or a flashing light, for example. In the case that two sensors are used, the alarm can be a beeper that generates sounds with different frequencies as different warning signals. Alternatively, a speaker is used to generate different kinds of music as different warning signals. A flashing light can be also used to generate different colors as different warning signals.
REFERENCES:
patent: 5169028 (1992-12-01), Morrison
patent: 5312039 (1994-05-01), Sayka et al.
patent: 5313818 (1994-05-01), Sayka et al.
patent: 5762684 (1998-06-01), Hayashi et al.
patent: 5905656 (1999-05-01), Wang et al.
Chang Ming Chago
Cho Ching Hua
Huang Yih Hwang
Lai Wei Hao
Huang Jiawei
J.C. Patents
Lefkowitz Edward
Macronix International Co. Ltd.
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