Coating apparatus – Program – cyclic – or time control
Reexamination Certificate
1999-06-21
2001-10-16
Bueker, Richard (Department: 1763)
Coating apparatus
Program, cyclic, or time control
C118S704000, C118S715000, C118S724000
Reexamination Certificate
active
06302962
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a diffusion system having an air curtain formation function for manufacturing semiconductor devices and a method of controlling the same, and more particularly, to a diffusion system having an air curtain formation function for preventing the loss of the heat inside the diffusion furnace by cutting off the loss of the heated air flow, and a method of controlling the same.
2. Background of the Related Art
Generally, semiconductor devices are manufactured by carrying out various fabrication processes repeatedly, and there are many types of main facility systems and supplementary facility systems for preforming these processes.
Among the various processes, a diffusion process includes an oxidation step for forming an oxide layer, and an annealing step for activating or stabilizing impurities such as boron (B) or phosphorus (P), which are implanted to provide electrical characteristics, etc.
The main facility system for the diffusion process is a furnace, which comprises a quartz tube and a heating chamber including a heater to heat the quartz tube; and the furnace has an opening for entry and removal of wafers.
In addition, a supplementary facility system for the furnace includes a process gas supplying unit for supplying a certain amount of process gas into the chamber; a boat elevator for loading/unloading a wafer boat having a plurality of wafers therein to the furnace; a wafer transfer unit for loading/unloading the wafers to the wafer boat; and a controlling unit for controlling the above components mechanically, etc.
After the wafer boat is loaded into the furnace through the opening, and the diffusion process is completed, the wafer boat is unloaded from the furnace through the opening, and the wafers loaded in the wafer boat are moved into a wafer transfer apparatus, such as a cassette, which will be moved to another fabrication system for a subsequent process.
Then, additional wafers to be processed are loaded into the wafer boat, the wafer boat is loaded into the furnace through the opening, and the diffusion process is carried out inside the furnace.
Generally, the furnace is continuously heated to maintain a constant temperature inside while the wafer boat is loaded or unloaded through the open opening. In addition, heaters are installed in some sections inside the furnace (e.g., upper section, middle section, lower section) to heat each respective section inside the furnace separately and maintain a uniform temperature throughout all sections. In addition, to control the temperature of the heater in each section of the furnace, there is provided a thermocouple (T/C) in each section inside the furnace.
However, in the conventional furnace, heated air flows out of the furnace through the open opening while the wafer boat is loaded/unloaded and the wafers therein are transferred, so that a large amount of heated air flow is lost through the opening, and the temperature uniformity is seriously deteriorated around the opening of the furnace. As a result, non-uniform thickness layers are formed on the semiconductor substrate due to the deteriorated temperature uniformity.
Therefore, in an effort to solve the problem, the temperature of the heater around the opening is raised to compensate for the temperature drop around the opening due to the flow of heated air through the opening. Alternatively, a cut-off door is installed to close a portion of the opening when the wafer boat has completely exited the furnace.
However, the conventional methods used to raise the temperature of the heater around the opening results in deterioration of the inner resistance of the heater, and a large amount of heat energy is still wasted because the loss of heated air is not prevented. Also, time is lost in compensating for the loss of the heated air flow and raising the inner temperature around the opening during the diffusion process.
In addition, while a cut-off door may close the opening and shut off the heated air flow coming out of the furnace while the wafer boat is completely removed from the opening, it cannot shut off the heated air flow while the wafer boat is being loaded or unloaded through the opening. In addition, the cut-off door is designed in a non-contact manner in order to prevent the generation of particles, and therefore, it can only partially shut off the heated air flow even when the cut-off door is in the closed position. Therefore, the cut-off door fails to stop the flow of heated air out of the furnace.
SUMMARY OF THE INVENTION
The present invention is directed to a diffusion system having an air curtain formation function for manufacturing semiconductor devices, and a method of controlling the same, for maintaining a uniform inner temperature inside a furnace. This uniform temperature improves the uniformity of the layers formed on a semiconductor substrate, increases the endurance of the furnace, and reduces the time for the temperature recovery, thereby improving the production yield of semiconductor devices.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the diffusion system having an air curtain formation function comprises a furnace having an opening through which a wafer boat having a plurality of wafers is loaded/unloaded; an air curtain apparatus for spraying a gas across the opening so as to form an air curtain cutting off the atmosphere inside of the furnace from the outside environment; and a controlling unit for controlling the air curtain apparatus by applying an on/off signal to the air curtain apparatus.
In addition, the air curtain apparatus may comprise a gas source for storing gas at a high pressure; a gas supply line in communication with the gas source; and a spray nozzle for spraying the gas supplied from the gas supply line at a high pressure.
In addition, a gas valve is provided on the gas supply line for opening/closing the gas supply line, and the controlling unit has a series of programs preset therein so as to control the gas valve by applying an on/off signal to the gas valve. A preheater may be further provided on the gas supply line for preheating the gas.
In addition, a plurality of spray nozzles are provided along the inside periphery of the opening at a constant interval such that the sprayed gas forms gas flow lines that traverse the opening in parallel and in one direction.
Alternatively, a plurality of spray nozzles are provided along the inside periphery of the opening such that the sprayed gas flow from one side of the opening traverses the opening from one side without conflicting with the sprayed gas flow from spray nozzles on the other side of the opening.
Alternatively, a plurality of spray nozzles may be provided along the inside periphery of the opening to spray the gas across the opening from all directions such that lattice-like gas flow traces are formed.
Alternatively, a plurality of spray nozzles may be radially provided along the inside periphery of the opening at a constant interval so as to spray gas toward the center of the opening.
In addition, the air curtain apparatus may further comprise an intake port for taking in the gas sprayed from the spray nozzle; a vacuum pump spaced apart from the intake port and forming a vacuum pressure therein; and a gas intake line connecting the vacuum pump and the intake port. In addition, the spray nozzle may be long, narrow and slit-shaped and formed on the end of the gas supply line.
Furthermore, the spray nozzles in each of the embodiments of the present invention are formed to spray gas upward toward the inside of the furnace at a certain angle.
In another aspect of the present invention, the method of controlling the diffusion system having an air curtain formation function may comprise the steps of forming an air curtain around an opening of a furnace by the operation of a controlling unit after the diffusion process has completed inside the furnace; moving a wafer boat out of the furnace with the a
Lee Yang-koo
Nam Ki-heum
Bueker Richard
Jones Volentine PLLC
Samsung Electronics Co,. Ltd.
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