Optics: measuring and testing – By particle light scattering – With photocell detection
Reexamination Certificate
2000-06-14
2003-03-11
Font, Frank G. (Department: 2877)
Optics: measuring and testing
By particle light scattering
With photocell detection
C356S339000, C356S342000
Reexamination Certificate
active
06532069
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-168968, filed Jun. 15, 1999, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a particle-measuring system that is mounted on a processing unit for forming a film on a semiconductor wafer by using a gas, and that measures the number of particles included in an exhaust gas discharged from the processing unit.
Generally, in the manufacturing of semiconductor integrated circuits, various kinds of processing units are used for processing semiconductor wafers (hereinafter to be referred to as wafers) as objects to be processed at various manufacturing stages, including a film deposition (CVD: chemical vapor deposition) process, thermal oxidation and impurity diffusion processes, an etching process, a film forming (sputtering) process, a thermal processing process, etc.
In the film forming process, thin films such as a silicon oxide (SiO
2
) film, a silicon nitride (SiN) film, and the like are deposited as insulation layers or insulation films on the surface of the wafer using, for example, a CVD unit. For forming wiring patterns and embedding trenches, thin films of tungsten (W), tungsten silicide (WSi), titanium (Ti), titanium nitride (TiN), titanium silicide (TiSi), etc. are deposited.
When these processing systems are used to carry out each processing, it is necessary to avoid as far as possible the generation of particles that become the cause of reduction in product yield.
Therefore, a particle-measuring system is installed on the processing system in order to real-time monitor the state of generation of particles within a processing chamber or in order to know the timing for cleaning the processing chamber. Particularly, in the film-forming system such as a CVD system or a sputtering system, there occurs an adhesion of unnecessary films onto the inner wall of the processing chamber or onto the surface of the parts. These unnecessary films are disposed and accumulated within the chamber during the film-forming process. These unnecessary films are easily peeled off at the next film-forming cycle, and particles are easily generated. Therefore, it has been important to monitor the volume of particles generated during the film-forming process.
One example of a processing system having a conventional particle-measuring system will be explained with reference to FIG.
18
.
A mounting table
4
for mounting a wafer W is provided inside a processing chamber
2
of almost a cylindrical shape, and a transmission window
6
made of quartz glass is disposed on the bottom of the chamber. A plurality of heating lamps
10
are disposed on a rotary table
8
below the transmission window
6
. Heating beams irradiated from these heating lamps
10
are transmitted through the transmission window
6
to heat the wafer W on the mounting table
4
.
A shower head
12
for introducing a processing gas such as a film-forming gas into the processing chamber
2
is provided on a chamber ceiling that faces the mounting table
4
. Four exhaust openings
14
(only two openings are shown in the drawing) disposed with approximately equal intervals are provided on the periphery of the bottom of the processing chamber
2
. Each of these exhaust openings
14
is connected to an exhaust pipe
16
extending downward.
Respective discharge sides of the exhaust pipes
16
are assembled into one, which is then connected to one absorption side of an assembling pipe
20
of a large diameter. A butterfly valve
18
for adjusting pressure is provided inside the assembling pipe
20
. A vacuum pump
22
is provided at a discharge side of the assembling pipe
20
, and a main exhaust pipe
24
of a relatively large diameter is connected to a discharge side of the vacuum pump
22
. Atmospheric air and a gas within the processing chamber
2
are exhausted to the outside by this vacuum pump
22
. A particle-measuring system
26
for counting the number of particles included in the exhaust gas is provided in the middle of the main exhaust pipe
24
.
FIG. 19
is a diagram showing a cross-sectional configuration of the main exhaust pipe
24
provided with the particle-measuring system
26
.
The particle-measuring system
26
has a laser beam irradiator
28
for emitting laser beams L and a stopper
32
for suctioning the emitted laser beams L disposed opposite to each other so that a line connecting between the two units pass through a center O of the main exhaust pipe
24
. Further, a scattered light detector
30
for detecting scattered lights SL generated by a collision of the laser beams L against particles P in the middle of the irradiation of the laser beams L, is disposed facing the center O of the main exhaust pipe
24
.
Based on this arrangement, for measuring the particles, the scattered light detector
30
detects the scattered lights SL that are generated when the laser beams L irradiated from the laser beam irradiator
28
have collided against the particles P that move within the main exhaust pipe
24
. The particle-measuring system
26
counts the number of the particles included in the exhaust gas based on this detection.
According to the above-described conventional processing unit, the particle-measuring system
26
is provided on the main exhaust pipe
24
at the discharge side of the vacuum pump
22
that assembles the exhaust pipes
16
from the processing chamber
2
together. of course, abnormalities of products adhere onto the inner walls of the exhaust pipes and blades of the pump and the valve due to the exhaust that occurs during the process from the processing chamber
2
to the particle-measuring system
26
. These adhered abnormalities are peeled off irregularly, and these generate new particles.
As the particles generated irregularly are added to the discharged particles that have actually been generated from within the processing chamber
2
, it has not been possible to accurately grasp the number of particles that have been generated from within the processing chamber
2
.
Further, the exhaust gas is swirled within the exhaust pipe near the discharge side of the vacuum pump
22
. Therefore, the same particles cross the laser beams repeatedly, and they are counted a plurality of times.
In principle, the actual number of particles within the processing chamber
2
should be highly correlated with the count number based on the measurement of particle by the particle-measuring system
26
. However, for the above reason, there is a very low correlation between the two data. Therefore, according to the conventional particle-measuring system, it has been difficult to accurately understand the state of particles actually generated from within the processing chamber
2
.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide a particle-measuring system capable of grasping a state of generation of particles by keeping high correlation between the number of particles generated and exhausted from within a processing chamber and the counted number of particles based on an accurate counting of the number of particles exhausted.
The present invention provides a particle-measuring system mounted on a processing system that has a processing unit for carrying out a predetermined processing of an object to be processed and an exhaust system for exhausting an atmospheric gas from within a processing chamber of the processing unit by a vacuum pump. Within the processing system, the particle-measuring system is installed on an exhaust pipe that forms a part of the exhaust system communicating between an exhaust opening of the processing chamber and the vacuum pump. With this arrangement, the particle measuring system measures the number of the particles included in the exhaust gas discharged from within the processing chamber.
The particle-measuring system is constructed of a laser beam irradiator for irradiating laser beams to within the exhaust pipe so that t
Ikeda Kyoko
Matsuda Tsukasa
Otsuki Hayashi
Font Frank G.
Punnoose Roy M.
Tokyo Electron Limited
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