Visual indicator cold trapping system

Details Visual indicator cold trapping system Visual indicator cold trapping system

2000-06-07

2004-10-05

Stoner, Kiley (Department: 1725)

Chemical apparatus and process disinfecting, deodorizing, preser

Chemical reactor

Waste gas purifier

C422S169000, C422S173000

Reexamination Certificate

active

06800254

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to apparatus for processing of a semiconductor wafer, and more particularly to a cold trapping system with a visual indicator to allow monitoring the adequacy of the cold trap.
BACKGROUND OF THE INVENTION
Semiconductor processes use vapor precursors for processing of thin films on an integrated circuit (IC) substrate. The majority of these vapor precursors, together with their by-products are pumping out and exhausted to a waste stream.
It is very expensive to collect and dispose of the precursor exhaust products. Further, these non-reactive precursors and these byproducts can be hazardous and harmful to the environment. The IC industry is forced to conform to ever more stringent regulations concerning the storage and disposal of these wastes.
It is very inconvenient to collect waste as a gas because it is difficult to transport and bulky to store. It is more convenient if the waste can be converted, at least partially into a solid or liquid waste. It is well known to use cold traps to completely condense some chemical vapors. It is also well known to use cold traps to condense elements of a precursor to at least simplify the waste collection process.
In a chemical vapor deposition (CVD) process, high temperature process is often used. Because of the low efficiency of the CVD process, a hot trap is recommended for completing the CVD reaction, leaving only the by-products to the exhaust stream. An example is copper CVD process. Copper CVD process uses copper-hfac-tmvs precursor to deposit copper on a hot surface (~200° C.) following the reaction:
2 Cu-hfac-tmvs→Cu+Cu(hfac)
2
+2 tmvs (at >~100° C.)
The reaction occurs at temperature higher than ~100° C. The efficiency of this reaction is roughly 10-20%, thus 80-90% of the precursor leaves the process chamber un-reacted. A cold trap would then collect the precursor Cu-hfac-tmvs, and the by-products Cu(hfac)
2
and tmvs. Using a hot trap before the cold trap, most of the precursor would further reacts, leaving only the by-products in the waste stream.
FIG. 1
shows a prior art apparatus for a cold trap. The precursor exhaust enters the cold trap at the cold trap input
23
, converting some elements of the exhaust into non-gaseous phase at the waste collection surface
15
, and exhaust the gaseous phase to the cold trap output
25
. The cooler means
37
serves to cool the waste collection surface
15
to a trapping temperature where the precursor exhaust reacts and separates into non-gaseous and gaseous components. The non-gaseous components trapping at the waste collection surface
15
could travel to the waste drain collection
45
. The waste collection
45
has a drain valve
43
to keep the waste stored.
The major disadvantage of this prior art is the inability to quickly evaluate the adequacy of the cold trap. If the cold trap is not efficient enough, material can travel downstream of the cold trap and might deposit outside of the cold trap. If there is some problem upstream of the cold trap, such as a cold section of the pipe leading to the cold trap, material can deposit outside of the cold trap.
A co-application titled “High pressure chemical vapor trapping system” of the same author, Tue Nguyen, provides a high pressure trapping system composing of a hot trap for completing the reaction and a cold trap for trapping the residue.
FIG. 2
shows the high pressure chemical vapor trapping system. The exhaust from the processing chamber
110
is pumped away by the vacuum pump
130
. The pressure in the process chamber foreline
115
is normally low, in the range of torr or millitorr pressure. After the vacuum pump, the pressure is almost atmospheric at the vacuum pump exhaust
135
. The hot trap
120
converts un-reacted precursors to the precursor by-products, and the cold trap
140
converts the gas phase by-products to non-gaseous phase by-products for easily transport and storage. This system connects to the downstream of the vacuum pump to take advantage of the high pressure at the pump exhaust. By not disturbing the chamber configuration, there is no potential contamination of the process. Using this system, there is no observable degradation to the vacuum pump, and no contamination to the process chamber.
There is no visual indicator to show whether or not the hot trap is converting all reaction elements, and there is no visual indicator that the cold trap is trapping all waste elements.
It would be advantageous if there is a visual indicator allowing the monitoring of the adequacy of the cold trap.
SUMMARY OF THE INVENTION
Accordingly, a visual indicator cold trapping system to allow monitoring the adequacy of the cold trap is provided. The system comprises a cold trap having an input port, a output port, a waste collection surface, a cooler means to cool the trap to a temperature in the range from 25 degrees to minus 200 degrees Celsius. The cold trap provides non-gaseous wastes at the waste collection surface, and gaseous exhaust at the gas output port. For visual indicator, the cold trapping system comprises a plurality of hollow transparent connectors.
In some aspects of the invention, the hollow transparent connector is connected to the input of the cold trap. Its transparency property allows the visual inspection of the cold trap for any material deposited there. Any material deposited in this transparent connector implies that there is problem upstream of the cold trap. Since there is material deposited in the connector section, it is likely that there is also material deposited in the pipe upstream of the cold trap. The visual indicator allows the problem to be spotted immediately and to alert the operator to take appropriate actions. In some aspects of the invention, the transparent connector has a heater means to bring its temperature to be the same as the upstream pipe. This allows the connector to be at the same temperature as the upstream pipe, thus eliminates the possibility of material deposition due to temperature difference. In some aspects of the invention, the input of the cold trap has a transparent section, served as the connector itself.
In some aspects of the invention, the hollow transparent connector is connected to the output of the cold trap. Any material deposited in this transparent connector implies that there is problem downstream of the cold trap. Since there is material deposited in the connector section, there is likely that there is material exhausted from the cold trap without being trapped there. In some aspects of the invention, the transparent connector has a heater means to bring its temperature to be the same as the downstream pipe. This allows the connector to be at the same temperature as the downstream pipe, thus eliminates the possibility of material deposition due to temperature difference.
In some aspects of the invention, the visual indicator cold trapping system further comprises a waste drain with a hollow transparent connector. In some aspects of the invention, the drain section is transparent to allow visual inspection of the collected material.
In other aspects of the invention, a high pressure chemical vapor trapping system to separate and collect elements of a chemical vapor exhaust with a visual indicator cold trap is provided. The system comprises a hot trap and a visual indicator cold trap connected to each other as a single unit. The exhaust pump is upstream of the trapping system, providing a high pressure in the hot trap.
The present invention system comprises a hot trap having an input port, a gas output port, a waste collection surface, and a heater. The heater heats the hot trap to a temperature in the range from 100 to 500 degrees Celsius. The hot trap accepts chemical vapor such as the above-described copper precursors and provides non-gaseous wastes at the waste collection surface, and gaseous exhaust at the gas output port at a pressure substantially the same as the input pressure.
The system also comprises a visual indicator cold trap having an input port operatively conne

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