Cleaning and liquid contact with solids – Processes – Combined
Reexamination Certificate
1999-04-01
2003-11-25
Stinson, Frankie L. (Department: 1746)
Cleaning and liquid contact with solids
Processes
Combined
C134S024000, C134S113000, C134S104100, C134S902000, C134S05600D
Reexamination Certificate
active
06652662
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of processing a substrate, such as a semiconductor wafer or a glass plate for an LCD, and a processing apparatus for carrying out the same.
2. Description of the Related Art
Generally, a semiconductor device fabricating process uses a cleaning system for clearing a surface of, for example, a semiconductor wafer (hereinafter referred to simply as “wafer”) of contaminants, such as particles, organic contaminants and metallic impurities, adhering to the surface. Usually, a single-wafer cleaning system is provided with a spin processor.
This prior art processor carries out a ‘scrub cleaning process’ to remove effectively particles adhering to the surface of a wafer. The scrub cleaning process brings a rotating end effector provided on its lower surface with a brush or a sponge pad into contact with a surface of a wafer held by a spin chuck to scrub off particles and the like adhering to the surface of the wafer. The processor has an arm capable of vertical movement and turning, and an air cylinder actuator held on the free end of the arm. A spindle capable of vertical movement and rotation is disposed below the air cylinder actuator, and the end effector is attached to the lower end of the spindle.
The air cylinder actuator exerts a vertical thrust through the spindle to the end effector to press the end effector against the surface of the wafer. A contact pressure (force exerted per unit area) actually applied to the surface of the wafer by the end effector is equal to the sum of the thrust exerted on the end effector and the weight of the end effector. If an excessively high thrust is applied to the spindle and the contact pressure exceeds a permissible limit, the surface of the wafer will be damaged. The arm is provided with a weight sensor capable of sensing the thrust acting on the spindle to avoid damaging the surface of the wafer. The vertical actuating operation of the air cylinder actuator is controlled automatically on the basis of data obtained by the weight sensor in order that the contact pressure applied to the wafer by the end effector may be controlled through the regulation of the thrust acting on the spindle.
Although the weight sensor employed in the prior art processor is able to sense the thrust acting on the spindle, the same is unable to measure the contact pressure of the end effector directly. Therefore, the weight sensor is incapable of sensing the variation of the contact pressure actually applied to the surface of the wafer by the end effector with respect to a predetermined contact pressure due to disturbances affecting the spindle, such as the frictional resistance of a bearing and torque for rotating the spindle.
A prior art processor disclosed in JP-A No. 8-267023 holds a wafer by a spin chuck formed by detachably attaching a mount to a rotating shaft. When measuring a contact pressure actually applied to the surface of the wafer, the mount is replaced with a sensor for sensing the contact pressure applied by an end effector. The contact pressure applied by the end effector to the wafer W can be measured by bringing the end effector into contact with the sensor in a manner in which the end effector is brought into contact with the surface of the wafer W.
The prior art processor disclosed in JP-A No. 8-267023, however, needs to attach the sensor to the rotating shaft to measure the contact pressure applied by the end effector. For example, when successively cleaning twenty-five wafers one at a time, it is impossible to ascertain, while the wafers are in process, that the contact pressure applied actually to the surfaces of the wafers is truly in coincidence with the predetermined level. If it is desired to measure the contact pressure, the cleaning process needs to be interrupted, which reduces the throughput of the cleaning process. Work for attaching the sensor to the rotating shaft requires additional time.
Rise in the level of integration of semiconductor devices requires the enhancement of the precision of contact pressure control. However, the prior art processor has difficulty in precisely controlling the contact pressure applied by the end effector through the measurement of the contact pressure during a cleaning process and the adjustment of the thrust acting on the spindle on the basis of measured data. It is possible such incapability of the processor reduces the reliability of the cleaning process.
The prior art processor has the arm capable of vertical movement and turning, the spindle capable of vertical movement and rotation and supported on the free end of the arm, and the end effector attached to the lower end of the spindle. The arm is turned and moved several times (at least twice) at least from the center of the wafer to the circumferential edge of the same to clean the surface of the wafer uniformly. Since the prior art processor uses only the single end effector throughout the cleaning process, it is possible that particles adhered to the end effector in an initial stage of the cleaning process, i.e., in a precleaning stage in which the surface of the wafer is cleaned with water, are transferred and adhere again to the surface of the wafer in a final stage of the cleaning process, i.e., in a finish cleaning stage, to reduce the cleaning effect of the cleaning process.
It is preferable, in view of satisfactorily achieving the cleaning process, to use an end effector provided with a cleaning member, such as a brush, suitable for cleaning the surface of the wafer provided with a film, such as an oxide film, a polysilicon film, an aluminum film or a nitride film. Since only the single end effector is supported on the arm, the processor is able to clean satisfactorily the surfaces of wafers provided with only limited kinds of films. Accordingly, a plurality of processors are needed for carrying out different cleaning processes for cleaning wafers respectively provided with different kinds of films.
Furthermore, the end effector detachably attached to the spindle needs to be replaced with a new one when the functional property of the end effector is changed, the end effector is deformed or the density of the working surface of the end effector is made irregular by the repetitive use of the end effector for the cleaning process. Replacing the worn end effector with a new one needs manual work, takes time and increases maintenance work.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a processing apparatus and a processing method capable of properly and easily obtaining accurate data on the contact pressure applied by an end effector to a workpiece while a process is being carried out.
Another object of the present invention is to provide a processing apparatus and a processing method capable of readily changing an end effector so as to meet the purpose of a process, use and the number of cycles.
With the foregoing object in view, according to a first aspect of the present invention, a processing apparatus comprises a holding means for holding a substrate, an end effector to be brought into contact with a surface of the substrate held by the holding means and capable of being retracted to a waiting position away from the surface of the substrate, and a measuring means for measuring contact pressure applied by the retracted end effector in the waiting position.
When successively processing a plurality of substrates by the processing apparatus in the first aspect of the present invention, the end effector is retracted to the waiting position after the completion of one cycle of a process for processing a substrate. Then, the measuring means measures directly the contact pressure applied by the end effector to see whether or not a normal contact pressure is applied to the surface of the substrate. If the measured result indicates that the normal contact pressure is applied to the substrate, the next substrate is processed. The process is continued until an abnormal contact pressure outside a permissible
Ishihara Akira
Miyazaki Takanori
Yonemizu Akira
Smith , Gambrell & Russell, LLP
Stinson Frankie L.
Tokyo Electron Limited
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