The present invention relates to thermal oxidation furnaces, CVD chambers and the like for forming material layers on a semiconductor wafer substrate during the fabrication of integrated circuits. More particularly, the present invention relates to a vacuum pump line having an alloyed nickel-chromium heater layer and connects a furnace, CVD chamber or the like to a vacuum pump to prevent condensation of residual powders in the vacuum pump line during evacuation of the furnace or chamber.
In the semiconductor production industry, various processing steps are used to fabricate integrated circuits on a semiconductor wafer. These steps include the deposition of layers of different materials including metallization layers, passivation layers and insulation layers on the wafer substrate, as well as photoresist stripping and sidewall passivation polymer layer removal. In modern memory devices, for example, multiple layers of metal conductors are required for providing a multi-layer metal interconnection structure in defining a circuit on the wafer. Chemical vapor deposition (CVD) processes are widely used to form layers of materials on a semiconductor wafer. Other processing steps in the fabrication of the circuits include formation of a photoresist or other mask such as titanium oxide or silicon oxide, in the form of the desired metal interconnection pattern, using standard lithographic techniques; subjecting the wafer substrate to a dry etching process to remove the conducting layer from the areas not covered by the mask, thereby leaving the metal layer in the form of the masked pattern; removing the mask layer using reactive plasma and chlorine gas, thereby exposing the top surface of the metal interconnect layer; cooling and drying the wafer substrate by applying water and nitrogen gas to the wafer substrate; and removing or stripping polymer residues from the wafer substrate.
CVD processes include thermal deposition processes, in which a gas is reacted with the heated surface of a semiconductor wafer substrate, as well as plasma-enhanced CVD processes, in which a gas is subjected to electromagnetic energy in order to transform the gas into a more reactive plasma. In CVD processes, as well as furnace processes such as silicon nitride processes, for example, exhaust gas that contains both reaction products and unreacted gas is discharged through an exhaust pipe system. During a vertical furnace silicon nitride process, for example, a reaction by-product such as ammonium chloride (NH4Cl) in the form of fine powder can easily deposit on any cold surface in the furnace or in the ducting system for the furnace.
A conventional CVD or furnace processing system includes a chamber for receiving a wafer. Process gases are introduced into the chamber to deposit material layers on the wafer. After completion of the process, the exhaust gases are evacuated from the chamber through an exhaust system including a vacuum pump line that typically includes valves and a vacuum pump. A tape heater typically surrounds the portion of the vacuum pump line extends between the chamber and the vacuum pump. During the exhaust evacuation process, the tape heater heats the interior of the vacuum pump line to maintain the exhaust gases in the gaseous state. A trap may be provided in the line to condense the exhaust gas into particles and trap the particles for removal.
If particles condense and adhere to the inside of the vacuum pump line, the valves, then the vacuum pump and other components in the exhaust system must be cleaned. Cleaning of the exhaust system typically involves troublesome operations including the removal of exhaust pipes, valves and vacuum pump, as well as cleaning of the pump. Moreover, if the reaction products are corrosive, they will have a tendency to corrode the exhaust pipes. Therefore, adhesion of the reaction products to the interior surfaces of the vacuum pump line and other components of the exhaust system must be minimized.
Use of a conventional tape heater to heat the vacuum pump line is attended by several drawbacks. First, the tape heater is expensive to install. Second; the tape heater is coiled around the line, forming gaps along the line. Therefore, the tape heater is typically incapable of uniformly heating the interior of the line. Consequently, exhaust gases may have a tendency to condense as powder on the lower-temperature areas of the line interior. Third, the tape heater is easily damaged and cannot be fixed but must be replaced. This introduces additional expense into maintenance of the CVD or furnace processing system. Fourth, disassembly of the tape heater for periodic maintenance is difficult.
Accordingly, a vacuum pump line with a novel heater layer for a CVD, furnace or other processing system is needed which is characterized by substantially uniform heating and can be repaired as needed to reduce the costs associated with maintenance of the CVD or furnace processing system.
An object of the present invention is to provide a vacuum pump line with a novel heater layer suitable for connecting a process chamber to a vacuum pump.
Another object of the present invention is to provide a vacuum pump with a novel heater layer having a nickel-chromium alloy.
Still another object of the present invention is to provide a novel vacuum pump line having a heater layer which is capable of providing substantially uniform heating capability along substantially the entire length of the vacuum pump line.
Yet another object of the present invention is to provide a vacuum pump line having a nickel-chromium heating layer which can be repaired as needed.
A still further object of the present invention is to provide a vacuum pump line having a novel cylindrical heater layer which is capable of applying substantially uniform heat to the vacuum pump line to prevent condensation of exhaust gases during transit through the line.
Another object of the present invention is to provide a method of fabricating a vacuum pump line having a heater layer, which method includes providing a pump line wall and may include sputtering or otherwise depositing a nickel-chromium alloy layer on the pump line wall or on an isolation layer provided on the
The present invention is generally directed to a novel vacuum pump line with heater layer suitable for a vacuum pump line of a process chamber. The vacuum pump line typically has a multi-layer construction including a heater layer sandwiched between a pair of isolation layers. The heater layer is typically a nickel-chromium alloy and cylindrical in configuration. As exhaust gases are distributed from a process chamber, through the vacuum pump line to a vacuum pump, for example, the heater layer is capable of distributing heat substantially uniformly along the vacuum pump line to prevent condensation of exhaust gases during transit through the line.
The present invention further includes a method of fabricating a vacuum pump line having a heater layer. The method includes providing a pump line wall and providing a nickel-chromium alloy heater layer in thermal contact with the pump line wall. Typically, an isolation layer is interposed between the heater layer and the pump line wall.
The invention will now be described, by way of example, with reference to the accompanying drawings, in which:
Referring initially to
As shown in
A typically cylindrical heater layer 16 encircles the inner isolation layer 14. The heater layer 16 is preferably a metal alloy of nickel and chromium, since nickel-chromium alloys have a high electrical corrosion resistance. Preferably, the heater layer 16 is sputtered on the inner isolation layer 14 using a nickel-chromium target in a conventional physical vapor deposition (PVD) chamber. As shown in
A typically cylindrical outer isolation layer 18 encircles the heater layer 16. Like the inner isolation layer 14, the outer isolation layer 18 is typically silicon dioxide, polytetrafluoroethylene (TEFLON), silicon rubber or any other suitable electrically-insulating and thermally-conductive material. The inner isolation layer 14 and the outer isolation layer 18 electrically insulate the heater layer 16 from the remaining portion of the vacuum pump line 10. A thermal insulation layer 20, which is typically silicon rubber, encircles the outer isolation layer 18.
Referring next to
An exhaust outlet opening 40 is typically provided in the bottom of the process chamber 32 for the evacuation of exhaust gases from the process chamber 32 during and/or after a process carried out on the wafer 38. Accordingly, one end of the vacuum pump line 10 is attached to the process chamber 32, with the gas flow bore 13 (
During operation of the wafer processing system 30, process gases 44 are introduced into the process chamber 32 through the GDP 34. Depending on the type of process, the process gases 44 form a material layer or layers (not shown) on the surface of the wafer 38. During and/or after completion of the process, the vacuum pump 42 draws exhaust gases 46 from the process chamber 32, through the vacuum pump line 10 to evacuate the exhaust gases from the process chamber 32. Simultaneously, electricity (typically 120 volts) is applied to the heater layer 16 (
Referring again to
Referring next to the flow diagram of
While the preferred embodiments of the invention have been described above, it will be recognized and understood that various modifications can be made to the invention and the appended claims are intended to cover all such modifications which may fall within the spirit and scope of the invention.