Abrading – Precision device or process - or with condition responsive... – Computer controlled
Reexamination Certificate
1999-12-13
2002-11-05
Rachuba, M. (Department: 3724)
Abrading
Precision device or process - or with condition responsive...
Computer controlled
C451S006000, C451S011000, C451S041000, C356S503000
Reexamination Certificate
active
06475062
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a film thickness measuring method measuring a film thickness of an element formation film formed on a substrate, a fabrication method of a thin film magnetic head having a planarization process for polishing and planarizing a surface of material to be polished and a substrate for forming a thin film magnetic head which forms a plurality of elements structuring the thin film magnetic head.
2. Description of the Related Art
In a fabrication of a thin film magnetic head used as a head for writing/reading of a magnetic disk drive, a chemical mechanical polishing (hereinafter, referred to a CMP) is used when a surface having a high flatness is formed. In the CMP, first, a polishing surface of a polishing pad covered on the rotating polishing surface plate and a surface to be polished of a substrate which is a material to be polished held on a polishing head are contacted with pressure. Then, supplying slurry, which is an abrasive material, on the polishing surface of the polishing pad, and respectively rotating the polishing pad and the polishing head, the slurry is supplied between the polishing pad and the surface to be polished, thereby polishing the surface to be polished chemically and mechanically. By this polishing using the CMP, a desired global flatness can be obtained along with a local flatness.
In the meantime, in a planarization process by a surface polishing using this CMP, it is extremely important, in a point to decide a performance of the completed elements, to control the polishing so that a polishing object film after polishing has a predetermined residual film thickness. Therefore, how to be able to measure the residual film thickness of the polishing object film at a high accuracy is a subject for a planarization process of the CMP.
In the past, a non-contact and contact film thickness measuring equipments have been used for the measurement of the residual film thickness of the polishing object film. As the non-contact film thickness measuring equipments, an optical film thickness measuring equipment named NanoSpec (product name: made by Nanometrics Japan), for example, exists. This non-contact optical film thickness measuring equipment inputs light to the film to be measured and then measures the film thickness of the film to be measured based on interference between a light reflected on the surface of the film to be measured and a light which transmits through the film to be measured and is reflected on the surface of a lower layer.
FIG. 10
shows a measuring method of the residual film thickness using the above non-contact optical film thickness measuring equipment in a process in the midst of a fabrication process of the thin film magnetic head. FIG.
10
(
a
) shows a rough state viewing an element
101
formed on the substrate from the top of the substrate. FIG.
10
(
b
) shows a cross section cut by a line A—A in FIG.
10
(
a
). First, a structure of the element
101
in the midst of the formation illustrated is briefly described. A bottom shielding layer
104
which is made of permalloy (NiFe), for example, and planarized by using the CMP is formed on an AlTiC substrate
102
. Though a description is omitted, an MR reading element and an insulating layer sandwiching the MR reading element are formed on the bottom shielding layer
104
. Then, a top shielding layer (a bottom pole: a bottom magnetic pole)
106
is formed by laminating and patterning permalloy on this insulating layer. Further, after embedding and coating the top shielding layer with alumina, a planarization is performed using the CMP. Then, a planarized layer made of the top shielding layer
106
and embedded layers
108
and
108
′ is formed.
In the meantime, a method for measuring the film thickness of the top shielding layer
106
formed as above by the non-contact optical film thickness measuring equipment is briefly described. A light beam formed by setting down a spot diameter
110
to approximately 20 &mgr;m is irradiated to the embedded layer
108
from this film thickness measuring equipment. A part of the light beam is reflected on the surface of alumina of the embedded layer
108
′ and the rest of the light transmits through the transparent alumina and is reflected on the surface of the bottom shielding layer
104
. The film thickness measuring equipment measures a film thickness of the embedded layer
108
′ by receiving and making these both reflection lights interfere. Since the upper surface of the bottom shielding layer
104
is planarized by the CMP and the top shielding layer
106
and the embedded layers
108
and
108
′ are planarized by the CMP as well, the film thickness of the embedded layer
108
′ shows the film thickness of the top shielding layer
106
. It will be noted that the film thickness of the insulating layer on the bottom shielding layer
104
is extremely so thin that the film thickness of the insulating layer on the bottom shielding layer
104
can be neglected or can be of course obtained as the top shielding layer
106
by reducing the known film thickness of the insulating layer from the measured value.
Thus, in the conventional film thickness measurement, the measurement is performed by irradiating the light beam of the non-contact optical film thickness measuring equipment on the surface in the element area during the formation. However, the recording density of the recent magnetic recording device is more and more improved, and finer and more complicated elements structuring the thin film magnetic head are further progressed along with this improvement. Therefore, it becomes more difficult to find a preferable position for the measurement on the element. In some case, the spot diameter
110
of the non-contact optical film thickness measuring equipment can not be fully entered in the irradiation area of the surface of the element during the formation. A portion of the light beam goes beyond the measurement area, thereby leading to a problem that the enough irradiation for the measurement is more difficult. As described above, the spot diameter
110
of the light beam described in
FIG. 10
is currently equal to approximately 20 &mgr;m. On the other hand, a dimension W
3
of the embedded layer
108
′ in the measurement area shown in
FIG. 10
is proceeded to be fined under 20 &mgr;m. If the current spot diameter is further reduced to accept the request of finer elements, a time is consumed for a positional confirmation before the measurement in the relationship with a measurement positioning accuracy, so that the reduction of the spot diameter is undesirable in mass-production because consequently a time required for the measurement becomes longer. If this problem is to be solved, the technical and cost burden for the film thickness measuring equipment increases, thereby leading to a higher cost of the thin film magnetic head.
Thus, in the conventional film thickness measuring method, a problem that the measurement of the residual film thickness in the polishing process such as the CMP becomes difficult accompanying to the finer and more complicated elements. Further, the difficulty of the film thickness measurement gives an influence on the mass-productivity of the elements. The more the difficulty of the film thickness measurement increases, the more a reduction of a yield in element fabrication is created. Furthermore, a throughput of the element fabrication is reduced because the time required for the film thickness measurement increases in the fabrication process, thereby leading to a possibility to create the quantity reduction of product supply.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a film thickness measuring method which can measure a residual film thickness of a polishing object film in a polishing process at a high accuracy.
Another object of the present invention is to provide a film thickness measuring method which can measure a film thickness at a high accuracy even if a measureme
Horinaka Takehiro
Kubota Toshio
Sugawara Masumi
Oliff & Berridg,e PLC
Rachuba M.
TDK Corporation
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