Electrical generator or motor structure – Dynamoelectric – Linear
Reexamination Certificate
1999-12-24
2001-11-27
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Linear
Reexamination Certificate
active
06323567
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a circulating system for shaft-type linear motors. The invention is particularly useful for maintaining an outer surface of a linear motor at a set temperature to control the effect of the motor on the surrounding environment and the surrounding components.
BACKGROUND
Linear motors are used in a variety of electrical devices. For example, linear motors are used in exposure apparatuses for semiconductor processing, other semiconductor processing equipment, elevators, electric razors, machine tools, machines, inspection machines, and disk drives.
Exposure apparatuses for semiconductor processing are commonly used to transfer images from a reticle onto a semiconductor wafer. A typical exposure apparatus utilizes one or more linear motors to precisely position a wafer stage holding the semiconductor wafer relative to the reticle. The images transferred onto the wafer from the reticle are extremely small. Accordingly, the precise positioning of the wafer and the reticle is critical to the manufacturing of the wafer. In order to obtain precise relative positioning, the reticle and the wafer are constantly monitored by a metrology system. Subsequently, with the information from the metrology system, the reticle and/or wafer are moved by one or more linear motors to obtain relative alignment.
One type of linear motor is a shaft type linear motor. A typical, shaft-type linear motor includes a magnet array that generates a magnetic field and a coil array that encircles the magnet array. The coil array includes a plurality of coils that are individually supplied with an electrical current. The electrical current supplied to the coils generates an electromagnetic field that interacts with the magnetic field of the magnet array. This causes the coil array to move relative to the magnet array. When the coil array is secured to the wafer stage, the wafer stage moves in concert with the coil array.
Unfortunately, the electrical current supplied to the coils also generates heat, due to resistance in the coils. Most linear motors are not actively cooled. Thus, the heat from the coils is subsequently transferred to the surrounding environment, including the air surrounding the linear motor and the other components positioned near the linear motor, The heat changes the index of refraction of the surrounding air. This reduces the accuracy of any metrology system and degrades machine positioning accuracy. Further, the heat causes expansion of the other components of the device. This further degrades the accuracy of the device. Moreover, the resistance of the coils increases as temperature increases. This exacerbates the heating problem and reduces the performance and life of the motor.
In light of the above, it is an object of the present invention to provide a system for maintaining an outside surface of a linear motor at a set temperature during operation. It is another object of the present invention to provide a system for cooling the coil array of a shaft-type linear motor. Still another object of the present invention is to provide an exposure apparatus capable of manufacturing high density semiconductor wafers.
SUMMARY
The present invention is directed to a circulating system for a coil assembly of a linear motor. The circulating system includes a coil housing and an inlet. The coil housing has a first body section that encircles the coil assembly and provides a fluid passageway around the coil assembly. The inlet extends into the fluid passageway and is in fluid communication with a fluid source. Fluid from the fluid source is directed or forced through the inlet into the fluid passageway. The present invention is particularly useful for cooling shaft-type linear motors that have a tubular shaped coil assembly.
Preferably, the rate of flow of the fluid to the fluid passageway is controlled to maintain an outer surface of the coil housing at a predetermined temperature. By controlling the outer surface temperature of the coil housing, heat transferred from the coil assembly to the surrounding environment can be controlled and/or eliminated. This minimizes the effect of the coil assembly on the surrounding environment.
The coil housing can also include a first end section, a second end section, and a second body section that cooperate to fully enclose the coil assembly and provide a fluid passageway which substantially surrounds the coil assembly. As provided herein, the coil assembly is positioned between the first body section and the second body section and between the first end section and the second end section.
Preferably, a plurality of spaced apart, coil supports are used to secure the coil assembly spaced apart from the coil housing. Each coil support is designed to have a relatively high ratio of surface area to volume. For example, a relatively small diameter pin can be used for each coil support. This allows the coil supports to easily dissipate heat to the fluid. Further, this minimizes direct thermal contact between the coil housing and the coil assembly and minimizes the heat transfer from the coil assembly to the coil housing. Additionally, the coil supports maximize the area of the coil assembly that is exposed for cooling with the fluid.
As provided herein, the coil supports can secure the coil assembly to the end sections. In this version, some of the coil supports extend between the coil assembly and the first end section and some of the coil supports extend between the coil assembly and the second end section to support the coil assembly between the end sections.
Additionally, the present invention includes an outlet that is in fluid communication with the fluid passageway. The outlet allows the fluid to be transferred from the fluid passageway back to the fluid source.
As number of alternate locations for the inlet and/or outlet are provided herein. For example, in one embodiment, the inlet extends into the fluid passageway near the first end section while the outlet extends into the fluid passageway near the second end section. In this embodiment, the fluid flows from near the first end section, through the fluid passageway along the length of the coil assembly and out the fluid passageway near the second end section.
In another embodiment, the invention includes a pair of spaced apart inlets. Each inlet extends into the fluid passageway near one of the end sections. The outlet extends into the fluid passageway intermediate the end sections. In this embodiment, the fluid enters into the fluid passageway near each end section. Subsequently, the fluid flows from each end section along approximately one-half of the coil assembly and exits the center of the coil assembly. With this embodiment, the coil supports near each end section are easily cooled with the fluid that is just entering the fluid passageway.
In another embodiment, the invention also includes a pair of spaced apart inlets. In this embodiment, one of the inlets is a primary inlet that extends into the fluid passageway near the first end section and one of the inlets is a secondary inlet that extends into the fluid passageway near the second end section. The outlet extends into the fluid passageway near the second end section. The fluid source supplies fluid at a greater rate to the primary inlet than the secondary inlet. In this embodiment, the secondary inlet provides additional fluid to cool the coil supports near the second end section.
In still another embodiment, the invention includes a separate, second fluid passageway near the coil assembly. In this embodiment, fluid from the fluid source is directed into the second fluid passageway. Preferably, the flow of fluid in the second fluid passageway is opposite from the flow of fluid in the other fluid passageway. More specifically, in the fluid passageway, fluid flows from the first end section towards the second end section. In the second fluid passageway, fluid flows from the second end section towards the first end section. This design allows for more uniform cooling because each end section recei
Hazelton Andrew J.
Ono Kazuya
Jones Judson H.
Nikon Corporation
Ramirez Nestor
Roeder Steven G.
Rose, Esq. Jim
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