Heating – With work cooling structure – Work holder having selectively usable heating and cooling...
Reexamination Certificate
2002-04-12
2004-06-08
Wilson, Gregory (Department: 3749)
Heating
With work cooling structure
Work holder having selectively usable heating and cooling...
C432S004000, C432S233000
Reexamination Certificate
active
06746238
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cooling system of a furnace, more particularly, to a multi-cycle cooling system, located by the furnace door. We can decrease the probability of pollution by particles and extend the lifetime of the furnace devices by using different liquid and gas cycles, cooling the different steps of the semiconductor processes in the furnace.
2. Description of the Prior Art
Thermal processing furnaces are used to provide high temperature processing of semiconductor based wafers which are placed within a gas filled processing chamber. Several silicon, silicon based or other types of wafers are typically used in manufacturing semiconductor thermal processing. To avoid the contact of wafers with human hands, the wafers are mechanically inserted into the furnace. In vertical atmospheric diffusion furnaces the wafers are usually inserted into a tower which is on top of a pedestal assembly. The pedestal assembly vertically transports the tower into a tubular shaped chamber of the furnace where the thermal processing occurs. Using a similar principle principle horizontal processing furnaces utilize a cantilever assembly which supports wafers therein. The cantilever assembly is transported along a horizontal axis into a horizontally oriented tubular shaped processing chamber. In either type of furnace, it is desired that the wafers be protected from exposure to undesirable gases to ensure proper thermal processing. For example, oxygen., water vapor and particulates found in air can react with the wafers and adversely affect their chemical and physical properties.
In order to ensure the purity of the reactions the processing chamber of the furnace must be adequately sealed. Therefore, in a thermal processing furnace the interface between the pedestal assembly and processing chamber is designed to prevent reactant gases, from within the processing chamber, from leaking therethrough. Typically, in thermal diffusion furnaces the pedestal assembly is sealed from the tubular processing chamber by an O-ring. Moreover, the tubular processing chamber is usually mounted on a base and is also sealed thereto by an O-ring.
In the present semiconductor processes, the thermal process is generally used in many different kinds of processes like the deposition process, oxidation process, and other kinds of processes. We must heat wafers to a temperature before the thermal process. Therefore, the furnace will still be a tool to be used in the thermal process in the present semiconductor process.
The furnace is separated into two types: One is a horizontal type furnace, and the other is a vertical type furnace. The basic structures of these two types are the same.
FIG. 1A
shows a structure diagram of the horizontal type furnace. At first, we put the wafers
10
which need heat treatment on the wafer boat
1
, which will be latter transported to the chamber by the paddle
12
. The chamber is inside the process tube
12
of the furnace. After the wafer boat
11
arrives at the correct place in the chamber, the door of the furnace
14
must be closed to prevent outside gases and tiny particles from entering into the chamber, not to pollute the wafers
10
. The closed door can also prevent the gases leaking out of the chamber from endangering workers when a chemical reaction, such as vapor deposition is taking place in the chamber. In order to make sure the temperature of the wafers are the same in the chamber, outside the process tube
13
, there is a heater
18
, which is used to adjust the temperature inside the chamber. This heater is often divided into several parts to adjust each temperature for different regions in the chamber, and also to increase the usability of the furnace.
FIG. 1B
shows a cross section diagram of the furnace. The objective of the heat treatment in the furnace is to proceed with the semiconductor processes like vapor deposition or thermal oxidation. The reactant, is transported through the fluid tube to the chamber by the fluid injector. The pump
19
and the tube
195
extract the by-products that are produced in the reaction process and the remnant reactants after the reaction. The tube
195
connects the process tube
13
and the pump
19
.
In order to make the contacting area between the door and the process tube airtight when the door
14
contacts the process tube
13
, the furnace uses a flange
17
and an end O-ring
142
on the process tube
13
and near the door
14
. The objective of the flange
17
is to create an airtight space after the door
14
closes on the process tube
13
. The objective of the end O-ring
142
is to prevent the gas inside the process tube
13
from leaking out.
The flange
17
on the process tube
13
near the door
14
is used to make the process tube
13
connect hermetically with the door, and to make sure that the process tube is an airtight place. Therefore, the end O-ring
142
must be assembled in the flange
17
to prevent the gas escaping out of the chamber from affecting the process in the process tube
13
. When the process temperature is higher, the materials of the end O-ring
142
lose their elasticity and will not have enough ability to seal up the crevice between the door
14
and the process tube
13
. Therefore, the flange
17
on the process tube
13
near the door
14
includes a cooling system to protect the end O-ring
142
. Especially in the high temperature processes inside the process tube
13
, we need cooling systems having higher efficiencies to extend the lifetime of the end O-ring.
FIG. 1C
shows part of a cross-section diagram of the furnace. Traditional flange
17
comprises the first flange
181
, the second flange
182
, the flange O-ring
183
, the end O-ring
142
, and the cooling system
184
which is located in the first flange
181
and the second flange
182
. This cooling system is a single-cycle system. The cooling liquid flows into the second flange
182
and flows out of the first flange
181
after the cycle. Obviously, the liquid cooling cycle is used for cooling and to prevent the flange O-ring
183
and the end O-ring from losing their capabilities in the high temperature process. In the traditional flange cooling system, the cooling liquid is usually used in water. The boiling point of the water is about 100° C., therefore the temperature of the place near the flange will be limited in the cooling liquid which flows in the cooling system and the temperature of the place near the flange will not be raised at will. In other words, the temperature of the place near the flange is lower than other places on the process tube.
In the semiconductor process like the deposition process or the thermal oxidation process, the gas in the process tube usually proceed in the chemical reaction and produce some by-products in the reaction process. Following the property of the by-product being different, the critical temperature which divides by-products into the vapor phase and the solid phase is different. When the condition of the temperature is higher, the probability of the by-products coming to the vapor phase is higher. When the conditions of the temperature is lower, the by-products come to the solid phase easier. The solid phase by-products deposit easily on the place around inside the process tube to affect the qualities of the wafer in the process.
In general, we usually use the pump
19
that is on the back-end of the process tube
13
to extract the by-products, which are produced in the semiconductor process, from the process tube
13
, but we can not extract the by-products from the process tube
13
absolutely. Sometimes, the remainder by-products in the process tube
13
are in the vapor phase, but sometimes the remainder by-products are usually in the solid phase depositing at the lower temperature place around inside the process tube. Furthermore, because we use pump
19
to extract the by-products from the process tube
13
, the solid phase by-products may be brought to the pump
19
or the tube
195
which connects
Chiang Kevin
Chu Eric
Tseng Ling-Hsin
Yew Ken
Dickinson Wright PLLC
United Microelectronics Corp.
Wilson Gregory
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