Measuring and testing – Sampler – sample handling – etc. – Automatic control
Reexamination Certificate
2000-06-05
2001-04-17
Noland, Thomas P. (Department: 2856)
Measuring and testing
Sampler, sample handling, etc.
Automatic control
C073S028010, C073S04050R, C073S863830, C073S864340
Reexamination Certificate
active
06216548
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a particle sampling apparatus and its operating method for semiconductor device manufacturing. More particularly, the present invention relates to a particle sampling apparatus for sampling particles directly from the processing chamber of a vacuum processor and its operating method.
2. Description of the Related Art
Semiconductor device manufacturing processes require very clean processing environments. Several manufacturing processes, including Low Pressure Chemical Vapor Deposition (LPCVD), Plasma Enhanced Chemical Vapor Deposition (PECVD), dry etch, sputtering, and ion injection, require a vacuum state during processing. The above processes are subject to various failures depending on the processing equipment is and the corresponding processing gas used. A great number of failures of semiconductor devices are caused by particles generated in a processing chamber. In order to determine how to minimize and contain these damaging particles, it is necessary to analyze and quantify the distribution of generated particles.
Conventionally, the particles and defects present on wafers are analyzed after the wafers are processed and removed from the chamber. However, it is often impossible to determine the exact cause of the damaging particles because the particles can not be observed during the sequence of events carried out in the chamber during a process.
An impactor is one conventional device that is capable of directly sampling particles from a processing chamber. However, a drawback of the impactor is that it is designed to sample such particles only while a high pressure process is being performed in the process chamber.
Referring to
FIG. 1
, an impactor or particle sampler
10
, collects particles by passing a gas released directly from inside the processing chamber through the sampler from the left inlet to the right outlet as designated by the arrows in FIG.
1
. Particle collection wafers are placed on stages
14
and
15
oriented perpendicular to the direction of gas flow. For example, the particle sampler
40
in
FIG. 1
has two stages, a first stage is
14
and a second stage
15
. A first nozzle
12
and a second nozzle
13
are formed facing stages
14
and
15
, respectively; and nozzles
12
and
13
have different diameters.
When a pressure gradient is applied from the left inlet to the right outlet of the particle sampler
10
, sample air containing particles passes through the first nozzle
12
, and collides with the collecting wafer on the first stage
14
by inertia so that the particles are collected according to the speed and the mass of the particles. Then, the sample gas that collided with the first stage
14
passes through the second nozzle
13
having a smaller diameter than that of the first nozzle
12
so that the gas and particles are accelerated. The accelerated particles collide with the collecting wafer on the second stage
15
. When the speed of the sample gas is sufficiently fast, very small particles will collide with, and can be collected on, the collecting wafer.
Conventionally, the impactor particle sampler is used for the collection of particles when the processing chamber is under high pressure. However, it cannot be used if the sampled gas is poisonous. If the processing gas in the processing chamber is poisonous, it must be replaced with a safer gas, such as nitrogen gas, before particle sampling is performed.
During vacuum processing, on the other hand, particle sampling can only be carried out using a vacuum pump to establish a pressure difference between the processing chamber and a pumping line downstream of the particle sampler. Particle sampling is accomplished using equipment with a sampling port that can be connected to the processing chamber, and a cut-off valve, a particle sampler, and another cut-off valve, installed in sequential order on a line from the sampling port. The sample gas is discharged through a discharge line by the vacuum pump. Then, while a vacuum process is performed in the processing chamber, the cut-off valves are opened for a certain time and some contents from the processing chamber are passed through the particle sampler where the particles are collected. The cut-off valves are then closed; then the particle sampler is disconnected from the processing chamber. Next, the collecting wafers are dismounted from the stages and particles on the collecting wafers are then analyzed.
If a vacuum process in the processing chamber is performed at a high enough vacuum, i.e., a low enough pressure, the vacuum pump of the particle collecting system can not maintain the proper pressure gradient. Then gas in the particle sampler may move in the opposite direction, carrying particles into the processing chamber. This condition is called back-flow, and it is undesirable because it increases the likelihood of damage to the semiconductor device in the processing chamber.
In addition, the particle sampler containing the collected particles must be completely purged before it is ready for subsequent use. After purging, the particle sampler must be reconnected to the processing chamber. However, the reconnecting task can again contaminate the particle sampler so that extra particles are introduced into the sampler. This can lead to a failure of the particle sampler to provide an accurate sample for analysis.
Thus there is a need for a particle sampling apparatus that can directly sample particles from a process chamber reliably, repeatedly and efficiently, whether the chamber is in a high pressure state or an extremely low pressure state. At high pressure, leaks must be prevented. At low pressure back-flow must be prevented. Purging must be leak proof and should not require disconnecting and reconnecting the apparatus to the chamber, to prevent contamination of the sampler after purging.
SUMMARY OF THE INVENTION
The present invention is directed to a particle sampling apparatus and its operating method having an internal purge system to provide reliable particle analysis. The present invention is further directed to maintaining a proper pressure difference between a high vacuum processing chamber and a pumping line. The present invention is also directed to preventing back-flow of sample gas into the processing chamber. The present invention is also directed to a particle sampling method that can be manual or automated.
To achieve these and other objects and advantages of the present invention a sampling apparatus for particle analysis comprises a sampling line including, in order, a sampling port, a sampling air valve, a particle sampler and an isolation valve, a pumping line connected between the isolation valve and a pump, and a discharge line is connected between the pump and a discharge port. The apparatus includes a purge line having, in order, a purge gas source, a purge air valve, and a divergence end. A purge-sampler line connects the divergence end to the sampling line between the sampling air valve and the particle sampler, and includes a purge-sampler air valve. A purge-pump line connects the divergence end to the pumping line, and includes a purge-pump air valve. The apparatus also includes an isolation valve bypass line connected at one end to the sampling line between the particle sampler and the isolation valve, connected at the other end to the pumping line between the isolation valve and the purge-pump line, and including a bypass air valve. A control unit controls the operation of the isolation valve, the pump, and the above named air valves.
Another aspect of the present invention is a method for sampling particles from a processing chamber used in the fabrication of semiconductor devices. The method includes establishing a predetermined driving pressure inside a pumping line at a pressure level lower than a predetermined process pressure of a process gas inside a processing chamber. The next step is prepurging a particle sampler on a sampling line connected between the processing chamber and the pumping line with a pu
Choi Baik-soon
Kang Sung-chul
Kim Jin-Sung
Park Hee-jung
Jones Volentine, L.L.C.
Noland Thomas P.
Samsung Electronics Co,. Ltd.
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