Abrading – Precision device or process - or with condition responsive... – With indicating
Reexamination Certificate
1999-01-19
2001-11-27
Hail, III, Joseph J. (Department: 3723)
Abrading
Precision device or process - or with condition responsive...
With indicating
C451S283000, C451S285000, C451S385000
Reexamination Certificate
active
06322422
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a measuring technology and, more particularly, to an apparatus for measuring local thickness of an insulating layer on a semiconductor wafer during a polishing and a polishing system using it.
DESCRIPTION OF THE RELATED ART
While a manufacturer is fabricating an integrated circuit on a semiconductor wafer, a semiconductor layer and an insulating layer are repeatedly deposited over the semiconductor wafer, and are patterned through a photolithography. The patterned layers deteriorate the step coverage, and the lower insulating layer is subjected to a polishing before deposition of a semiconductor layer. If the lower insulating layer is polished too much, the insulating layer can not offer good electrical isolation, and the detection of remaining thickness is important.
A typical example of the apparatus for measuring the thickness of the remaining insulating layer is disclosed in Japanese Patent Publication of Unexamined Application Ser. No. 4-357851, and
FIG. 1
illustrates the prior art measuring apparatus.
The prior art measuring apparatus is used for a semiconductor wafer
1
. An insulating layer
2
has been already deposited on the semiconductor wafer
1
, and is now being polished on a polishing pad
3
. Polishing slurry
4
is supplied onto the polishing pad
3
, and the polishing pad
3
is rotating with respect to the insulating layer
2
.
The prior art measuring apparatus comprises a measuring electrode
5
, a protective electrode
6
and an insulating layer
6
a
, and the measuring electrode and the protective electrode
6
are embedded in the polishing pad
3
. The measuring electrode
5
and the protective electrode
6
are exposed to the polishing slurry
4
. The measuring electrode
5
is spaced from the protective electrode
6
, and the insulating layer
6
a
electrically isolates the measuring electrode
5
from the protective electrode
6
.
The prior art measuring apparatus further comprises a measuring section
7
and an amplifier
8
. The measuring section
7
is directly connected to the measuring electrode
5
and to the non-inverted input node of the amplifier
8
. The output node of the amplifier
8
is connected to the protective electrode
6
and the inverted input node. A parasitic capacitor
9
is connected to the back surface of the semiconductor wafer
1
. The measuring section
7
supplies an alternating current signal DT
1
to the measuring electrode
5
and the non-inverted input node. The amplifier
8
shifts the phase of the alternating current signal DT
1
by 180 degrees, and produces an inverted alternating current signal CDT
1
.
While the insulating layer
2
is being polished, the measuring section
7
supplies the alternating current signal DT
1
to the measuring electrode
5
, and the inverted alternating current signal CDT
1
is supplied to the protective electrode
6
for bootstrapping. The alternating current signal DT
1
varies the amplitude in proportion to the thickness of the insulating layer
2
, and the measuring section
7
produces an output signal OUT
1
indicative of the thickness of the remaining insulating layer
2
.
The prior art measuring apparatus merely measures an average thickness. The semiconductor wafer
1
is getting large, and the manufacturer hardly polishes the insulating layer
2
uniformly. This means that the insulating layer
2
is locally different in thickness from the average thickness. The prior art measuring apparatus can not measure the locally different thickness. This is the first problem inherent in the prior art measuring apparatus.
The second problem is undesirable damage to the circuit components fabricated on the semiconductor wafer
1
. When the alternating current signal DT
1
is applied to the measuring electrode
5
, the electric field extends over the semiconductor wafer
1
. The electric field is liable to damage the circuit components.
SUMMARY OF THE INVENTION
It is therefore an important object of the present invention to provide a measuring apparatus, which can measure the thickness of an arbitrary portion of an insulating layer without damages to circuit components.
It is also an important object of the present invention to provide a polishing system, which realizes an insulating layer with completely uniform thickness.
In accordance with one aspect of the present invention, there is provided an apparatus for measuring a thickness of an insulating layer having a first surface held in contact with a first electrode means and a second surface opposite to the first surface and held in contact with a non-conductive liquid spread over a moving member, and the apparatus comprises a second electrode means stationary with respect to the moving member, changing a relative position with respect to the first electrode means and a first distance to the first electrode means together with the moving member and forming a first capacitor together with first electrode means, the insulating layer and the non-conductive liquid, a third electrode means stationary with respect to the insulating layer and with respect to the first electrode means, a fourth electrode means stationary with respect to the moving member, changing a second distance to the third electrode means and forming a second capacitor together with the third electrode means and the non-conductive liquid, a source of electric power connected between the first and third electrode means and the second and fourth electrode means, a measuring equipment connected to the second electrode and the fourth electrode for measuring a first capacitance between the first electrode means and the second electrode means and a second capacitance between the third electrode means and the fourth electrode means and a calculating means connected to the measuring equipment for determining a thickness of the insulating layer on the basis of the first capacitance and the second capacitance.
In accordance with another aspect of the present invention, there is provided a polishing system for polishing an insulating layer formed on a semiconductor wafer, and the polishing system comprises a measuring means for measuring a thickness of more than one portion of the insulating layer, a polishing pad for polishing a surface of the insulating layer, a feeding means for supplying non-conductive polishing slurry between the polishing pad and the surface of the insulating layer, a pressurizing means exerting variable force on a plurality of portions of the semiconductor wafer for pressing the insulating layer against the polishing pad and a controlling means connected to the measuring means and the pressurizing means for instructing the pressurizing means to vary the variable force at the plurality of portions depending upon the thickness of the more than one portion of the insulating layer.
REFERENCES:
patent: 5492594 (1996-02-01), Burke et al.
patent: 5562529 (1996-10-01), Kishii et al.
patent: 5851135 (1998-12-01), Sandhu et al.
patent: 5916009 (1999-06-01), Izumi et al.
patent: 5961369 (1999-10-01), Bartels et al.
patent: 6007405 (1999-12-01), Mei
patent: 58-115618 (1983-07-01), None
patent: 1-207929 (1989-08-01), None
patent: 1-306073 (1989-12-01), None
patent: 4-357851 (1992-12-01), None
patent: 9-134904 (1997-05-01), None
patent: 10-233-421 (1998-09-01), None
Berry Jr. Willie
Hail III Joseph J.
Laff, Whitesel & Saret Ltd
NEC Corporation
Whitesel J. Warren
LandOfFree
Apparatus for accurately measuring local thickness of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus for accurately measuring local thickness of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus for accurately measuring local thickness of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2583829