Abrading – Precision device or process - or with condition responsive... – By optical sensor
Reexamination Certificate
2000-07-26
2002-06-25
Morgan, Eileen P. (Department: 3723)
Abrading
Precision device or process - or with condition responsive...
By optical sensor
C451S010000, C451S011000, C451S041000, C451S054000, C451S287000
Reexamination Certificate
active
06409576
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polishing apparatus for polishing a workpiece such a semiconductor substrate, and more particularly to a polishing apparatus having a measuring function for accurately measuring a thickness of a surface layer of the workpiece which has been polished.
2. Description of the Related Art
In manufacturing processes of semiconductor substrates, a polishing apparatus has been employed for polishing a surface of a semiconductor substrate (workpiece) to a flat mirror surface. Such a polishing apparatus comprises a polishing section for polishing a semiconductor substrate by pressing a surface of the semiconductor substrate against a turntable having a polishing surface thereon while the semiconductor substrate and the polishing surface are relatively being moved, and a cleaning section for cleaning the semiconductor substrate which has been polished by the polishing section.
As semiconductor devices become more highly integrated in recently years, circuit interconnections on semiconductor substrates become finer and the distance between those circuit interconnections becomes smaller. However, when semiconductor substrates are processed, particles such as particles of semiconductor material, dust particles, crystalline protrusive particles, or the like often tend to be attached to the semiconductor substrates being processed. If a particle larger than the distance between interconnections exists on a semiconductor substrate, then the particle will short-circuit interconnections on the semiconductor substrate. Therefore, particles on a semiconductor substrate have to be sufficiently smaller than the distance between interconnections on the semiconductor substrate. To meet this demand, there has been required the technology for removing fine particles or submicronic particles from semiconductor substrates in the cleaning section.
As a cleaning method in the cleaning section, there has heretofore been known a scrubbing cleaning process of scrubbing a surface of a semiconductor substrate with a brush of nylon, mohair or the like, or a sponge of polyvinyl alcohol (PVA). Further, there has been known other processes, including an ultrasonic cleaning process of cleaning a semiconductor substrate by ejecting water having ultrasonic vibrational energy to a surface of the semiconductor substrate, a cavitation jet cleaning process of cleaning a semiconductor substrate by ejecting water containing cavitation to a surface of the semiconductor substrate, and the like. A cleaning process which combines two or three of the above processes is more effective in removing fine particles from the semiconductor substrate. Therefore, a plurality of cleaning machines for conducting such cleaning processes are often arranged in the cleaning section of the polishing apparatus.
On the other hand, a film thickness measuring device, e.g., an inline thickness measurement device (ITM), for measuring a film thickness, i.e., a thickness of a surface layer of a semiconductor substrate which has been polished is often incorporated in the cleaning section besides the above cleaning machines.
However, the above conventional cleaning machine does not have a mechanism for detecting the reference position on a semiconductor substrate, which may be represented by an orientation flat or a notch, and aligning the semiconductor substrate with a certain direction. In addition, the film thickness measuring device does not have a mechanism for detecting the reference position on a semiconductor substrate and aligning the semiconductor substrate with a certain direction.
Therefore, measuring points on the semiconductor substrate at which a thickness of the surface layer is to be measured by a film thickness measuring device cannot be accurately recognized in the present condition. In the some cases, although the rectangular direction of a semiconductor substrate is recognized by an image processing, the measuring points cannot be accurately specified by the image processing.
In order to solve the above problems, an additional device for aligning the reference position on a semiconductor substrate with a certain direction is required. However, such an additional device not only causes higher cost, but also makes a polishing apparatus larger.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above drawbacks. It is therefore an object of the present invention to provide a polishing apparatus which can accurately measure a film thickness of the workpiece which has been polished.
According to an aspect of the present invention, there is provided a polishing apparatus for polishing a surface of a workpiece, comprising: a polishing section for polishing a surface of a workpiece; a cleaning section for cleaning a polished surface of the workpiece; a rotating mechanism for rotating the workpiece during cleaning or after cleaning; a sensor for detecting a reference position of the workpiece; a controller for controlling the rotating mechanism to stop the workpiece against rotation to align the reference position with a predetermined position based on a detecting signal from the sensor; and a film thickness measuring device for measuring a thickness of a polished surface layer of the aligned workpiece.
With the above arrangement, the workpiece which has been polished by the polishing section is rotated during cleaning or after cleaning by the rotating mechanism, and the controller controls the rotating mechanism to stop the workpiece against rotation to align the reference position with a predetermined position. Therefore, since the workpiece which has been cleaned by the cleaning section is aligned with the predetermined direction, the film thickness measuring device can accurately measure a film thickness at the predetermined measuring points.
In a preferred aspect of the present invention, the rotating mechanism is incorporated in a cleaning machine, and the workpiece is cleaned or dried while the workpiece is rotated by the rotating mechanism. On the other hand, the rotating mechanism may be incorporated in other devices which operate the workpiece after cleaning, e.g., the film thickness measuring device.
In a preferred aspect of the present invention, the controller controls the rotating mechanism to control a rotational speed of the workpiece.
The controller may lower a rotational speed of the workpiece when the reference position of the workpiece is detected by the sensor.
In a preferred aspect of the present invention, the controller controls the rotating mechanism to control a rotational speed of the workpiece based on an elapsed time since the detection of the reference position by the sensor.
Preferably, the sensor may comprise a photosensor.
According to another aspect of the present invention, there is provided a polishing method for polishing a surface of a workpiece, comprising: polishing a surface of a workpiece; cleaning a polished surface of the workpiece; aligning a reference position of the workpiece with a predetermined position; and measuring a thickness of the polished surface layer of the aligned workpiece.
The above and other objects, features, and advantages of the present invention will be apparent from the following description when taken in conjunction with the accompanying drawings which illustrates preferred embodiments of the present invention by way of example.
REFERENCES:
patent: 5679055 (1997-10-01), Greene et al.
patent: 5679060 (1997-10-01), Leonard et al.
patent: 6004187 (1999-12-01), Nyui et al.
patent: 6132289 (2000-10-01), Labunsky et al.
Inoue Masafumi
Oguri Syozo
Takahashi Mei
Takahashi Saburo
Ebara Corporation
Morgan Eileen P.
Takahashi Mei
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