Cleaning and liquid contact with solids – Apparatus – With alarm – signal – indicating – testing – inspecting,...
Reexamination Certificate
2000-06-19
2002-09-10
Gulakowski, Randy (Department: 1746)
Cleaning and liquid contact with solids
Apparatus
With alarm, signal, indicating, testing, inspecting,...
C134S201000, C134S902000
Reexamination Certificate
active
06446647
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cassette holder, and more particularly, to a cassette holder for cleaning equipment.
2. Description of the Prior Art
In current semiconductor processes, automatic cleaning equipment is some of the most fundamental and common fabrication equipment. The automatic cleaning equipment uses a robot to move a cassette carrying semiconductor wafers between acid tanks and water tanks, automating surface cleaning of the semiconductor wafers. To prevent the robot from losing the cassette, a loading plate is usually placed at the bottom of the acid or water tank. The loading plate prevents the cassette from moving, and thus prevents it from being misplaced and hence irretrievable to the robotic arm.
Please refer to FIG.
1
.
FIG. 1
is a schematic diagram of automatic semiconductor cleaning equipment
10
according to the prior art. The cleaning equipment
10
comprises a robot (not shown), a solution tank
12
, a plurality of pipes
14
positioned on an internal wall of the solution tank
12
, a cassette
16
in which a plurality of semiconductor wafers are placed, and a cassette holder
20
in the solution tank
12
. The cassette holder
20
can hold two cassettes
16
. The pipes
14
usually comprise a thermal couple thermometer
22
, a barometric level sensor
24
, a heater
26
, a supply pipe
28
and an aspirator
30
. The cleaning equipment
10
is usually equipped with three or four heaters
26
, though
FIG. 1
shows only one heater
26
.
The cassette holder
20
comprises a loading plate
32
, a plurality of guide blocks
34
mounted on the loading plate
32
, and a plurality of feet
36
supporting the loading plate
32
. The cassette holder
20
uses guide blocks
34
, two in each direction, to prevent any displacement of the cassette
16
.
In semiconductor processes, a hot-acid solution is usually used as an etching or cleaning solution. The solution tank
12
, therefore, is made of quartz, which is resistant to both heat and acid. Similarly, the loading plate
32
is formed by welding quartz rods together (usually called a quartz frame). Such a frame is resistant to the hot-acid solution. The cassette holder
20
is quite light, and may be uplifted by the underlying heater
26
, or by buoyancy. In overcome buoyancy of the cassette holder
20
, the loading plate
32
is often made of large-diameter quartz rods to increase its weight and improve its structural integrity. However, in the event of errors or accidents the thicker quartz rods may cause the solution tank
12
crack. For example, the robot may fail to remove the cassette
16
from the solution tank
12
, and another cassette is then put into the solution tank
12
on top of the cassette
16
. Overloading of cassettes can cause serious damage to the cassette holder
20
, such as breaking the loading plate
32
.
Furthermore, although a Teflon holding plate
38
is employed to fix each of the pipes
14
to the top of the wall of the solution tank
12
, the bottoms of the pipes
14
that extend into the solution tank
12
are not sufficiently restricted. After the pipes
14
have been exposed to the hot-acid solution for a period of time, the bottoms of the pipes
14
may distort and push against the cassette
16
, leading to misplacement of the cassette
16
. This, in turn, can lead to accidents during the automatic transfer process.
In order to prevent the acid solution from evaporating, a hood (not shown) covers the solution tank
12
. This hinders the operator from observing the solution level in the solution tank
12
. The operator can check the solution level only when the hood is opened, but the operator must check the level quickly as the hood closes in a short while after the cassette
16
is placed into the solution tank
12
. The solution tank
12
does employ the barometric level sensor
24
to check the level of the acid solution in the solution tank
12
. The barometric level sensor
24
is full of nitrogen gas. Different solution levels cause different gas pressures within the barometric level sensor
24
. A level panel (not shown) uses a set of six variable resistors to generate the level signal.
In practice, however, there is no steady reference point for the solution level. Most operators adjust the solution level based upon experience. Thus, the solution level isn't controlled precisely and scientifically. If the solution level is too high, the acid solution is wasted and may flow over the solution tank
12
. If solution level is too low, the upper portion of the wafer
18
may lack sufficient chemical treatment, causing defects to the wafer
18
.
SUMMARY OF THE INVENTION
It is therefore a primary objective of the present invention to provide a cassette holder for cleaning equipment to solve the above-mentioned problem.
In a preferred embodiment, the present invention provides a cassette holder positioned in cleaning equipment. The cleaning equipment comprises a solution tank, at least one pipe positioned on an internal wall of the solution tank, and at least one cassette in which at least one semiconductor wafer is placed. The cassette holder has a loading plate in the solution tank for holding the cassette. There are pluralities of guide blocks mounted on the loading plate to prevent movement of the cassette, and a side-frame positioned at an end of the loading plate proximate to the pipe. The side-frame is designed for disassembly and serves as a shield between the pipe and the cassette that prevents the pipe from pushing against the cassette. The side-frame comprises a horizontal rod that serves as a level index for the solution tank. The bottom of the loading plate has a plurality of neck feet, and once a neck foot suffers a force that exceeds a normal value, the neck foot will break. A Teflon tube that enhances the support strength of the neck foot covers each neck foot. The cassette holder further comprises at least one weight to overcome buoyancy of the cassette holder.
It is an advantage of the present invention that the cassette holder has the side-frame that prevents the pipe from pushing against the cassette. The side-frame includes the horizontal rod that serves as a level index for the solution. The bottom of the loading plate has a plurality of neck feet, which prevents the loading plate from impacting the solution tank during accidents in the transfer process. The cassette holder uses the weight to overcome buoyancy of the cassette holder.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the various figures and drawings.
REFERENCES:
patent: 3521413 (1970-07-01), Scott et al.
patent: 5547515 (1996-08-01), Kudo et al.
patent: 6116254 (2000-09-01), Shiramizu
patent: 01012534 (1989-01-01), None
patent: 03209822 (1991-09-01), None
patent: 03256326 (1991-11-01), None
patent: 05129268 (1993-05-01), None
Chang Hung-Hsien
Chu Eric
Chung Chin-Wen
Hsu To-Yao
Yang Hsing-Sheng
Gulakowski Randy
Hsu Winston
Perrin Joseph
United Microelectronics Corp.
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