Heater lift lead screw for vertical furnaces

Details Heater lift lead screw for vertical furnaces Heater lift lead screw for vertical furnaces

2002-01-11

2002-11-19

Walberg, Teresa (Department: 3742)

Electric heating

Heating devices

Combined with container, enclosure, or support for material...

C392S418000, C414S936000, C118S729000, C432S239000

Reexamination Certificate

active

06483082

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to vertical furnaces as used in semiconductor manufacture in general and more particularly to the lift mechanism for moving the heater into and out of the furnace.
BACKGROUND OF THE INVENTION
Various lifts and elevators as used in vertical furnaces use variations of vertical spiral drives for moving the lift or elevator. In U.S. Pat. No. 6,168,427 issued on Jan. 2,2001 and entitled “Apparatus for Guiding the Removal of a Processing Tube From a Semiconductor Furnace” teaches a semiconductor wafer boat elevator including a boat support coupled by a lateral arm to a vertical spiral drive which moves the elevator up and down, beneath the furnace. This patent is assigned to a common assignee.
U.S. Pat. No. 6,171,453 issued on Jan. 9,2001 and entitled “Alignment Mark Shielding Ring and Method of Using” shows a wafer pedestal elevator to move the wafers into and out of the processing chamber. The movement of the elevator is typically by a vertical spiral drive. This patent is assigned to a common assignee.
U.S. Pat. No. 6,095,806 issued on Aug. 1,2000 entitled “Semiconductor Wafer Boat and Vertical Heat Treating System” teaches the use of a ball screw to move a transfer base in a vertical direction. The transfer base is guided in the vertical direction by two guide rails. In addition, another ball screw is used to move an arm carrying the wafer boat. The arm moves into and out of a processing chamber that is sealed.
In most all of the various lift lead screw mechanism, the backlash tolerance in the lead screw give rise to positioning problems. Such positioning problems create wafer scrap and lead to a maintenance program that is frequently causing the lift to be off-line. In addition the starting torque of the lift mechanism is high and the actual running of the lift mechanism along its shaft is not as smooth as desired.
SUMMARY OF THE INVENTION
These and other operational problems are substantially reduced and even eliminated in the following vertical semiconductor furnace a heater lift lead screw having a multiple diameter shaft with a first tubular bearing surface at a first end. At the opposite end of the shaft is an elongated tubular surface.
A pillow block support receives the first tubular bearing surface of the shaft and supports the shaft for rotation. A motor is positioned axially in line with the pillow block support and receives the elongated tubular surface of the shaft. The motor provides the power to rotate the shaft either a clockwise or counterclockwise direction in the pillow block support.
The shaft has a threaded portion intermediate the first and second ends of the shaft. The threaded portion has a diameter that is larger than the diameter of the first bearing surface and the elongated tubular surface. A linear actuator member with an axially extended internal threaded portion is threadably mounted on the threaded portion of the shaft for transverse travel along the threaded portion under the control of the motor. A flange is mounted on the linear actuator in a position that is transverse to the axially extended threaded portion of the shaft. The flange supports a platform that carries furnace heater into and out of the furnace in the preferred embodiment.


REFERENCES:
patent: 5407350 (1995-04-01), Iwabuchi et al.
patent: 5658115 (1997-08-01), Yamazaki et al.
patent: 5697749 (1997-12-01), Iwabuchi et al.
patent: 5984607 (1999-11-01), Oosawa et al.
patent: 6368040 (2002-04-01), Yamasaki et al.

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