Abrading – Abrading process – Abradant supplying
Reexamination Certificate
1999-12-23
2001-07-10
Banks, Derris H. (Department: 3723)
Abrading
Abrading process
Abradant supplying
C451S446000
Reexamination Certificate
active
06257965
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polishing liquid supply apparatus usable for a chemical mechanical polishing (CMP) apparatus, which is usable in a semiconductor device production process for smoothing a surface of a semiconductor device.
2. Description of the Related Art
In response to the increasing degree of integration, it has become increasingly important to smooth a surface of a wafer of a semiconductor device during the production process thereof. The wafer surface can be smoothed by a CMP apparatus. When the CMP apparatus is used, the wafer surface can be smoothed by a chemical mechanical polishing method which utilizes an interaction of mechanical polishing by a polishing pad and a polishing agent contained in the polishing liquid or slurry and chemical etching by a solution of slurry.
Recently, a so-called dicing machine method and a trench method have been widely used, by which a patterned film is buried in a wafer formed of a metal, dielectric or other material which is different from the material of the film, and the film is treated with chemical mechanical polishing. As a result, a wafer having a desired pattern of film buried therein is formed.
In such chemical mechanical polishing, the chemical properties of a polishing liquid used need to be strictly controlled in such a manner that the rate of polishing the film material is appropriate. The pH of the polishing liquid, which is closely related to the polishing speed, is especially important.
Conventionally, there is an attempt to stabilize the amount of the polishing liquid supplied to a chemical mechanical polishing apparatus from a polishing liquid supply system.
For example, Japanese Laid-Open Publication No. 9-131660 describes a semiconductor device production apparatus
700
as shown in
FIG. 7
including a chemical mechanical polishing apparatus. The semiconductor device production apparatus
700
includes a polishing liquid tank
701
for storing a polishing liquid
2
used for polishing a semiconductor wafer or the like, crude polishing liquid tanks
713
a
and
713
b
connected to the polishing liquid tank
701
respectively through pipes
711
a
and
711
b
and pumps
712
a
and
712
b
, a chemical mechanical polishing apparatus
716
connected to the polishing liquid tank
701
through a pipe
709
and a pump
710
, and a waste liquid treating apparatus
717
connected to the polishing liquid tank
701
through a pipe
714
and a pump
715
.
The polishing liquid tank
701
accommodates a liquid level sensor
704
for measuring the amount of the polishing liquid
2
and a stirring device
708
for appropriately stirring the polishing liquid
2
. A control section
707
is connected to the liquid level sensor
704
, the stirring device
708
, and a pH sensor (not shown) accommodated in the chemical mechanical polishing apparatus
716
. The pH sensor is provided on an adsorption plate (not shown) for adsorbing a wafer accommodated in the chemical mechanical polishing apparatus
716
. The polishing liquid
2
in the polishing liquid tank
701
is supplied to the chemical mechanical polishing apparatus
716
by the pump
710
through the pipe
709
.
Before the wafer is polished, the pH sensor measures the pH of the polishing liquid
2
. The driving amount of the pump
710
is adjusted based on the pH measured, and thus the amount of the supplied polishing liquid
2
is controlled.
Japanese Laid-Open Publication No. 7-233933 describes a polishing liquid supply apparatus
800
shown in FIG.
8
. The polishing liquid supply apparatus
800
includes a mixer
801
for mixing the polishing liquid
2
with an additive liquid, a polishing liquid tank
802
connected to the mixer
801
, an additive liquid supply pipe
806
for supplying the additive liquid to the mixer
801
via a control valve
807
, and two detection pipes
811
and
812
inserted into the polishing liquid tank
802
at a level difference of H. The detection pipes
811
and
812
respectively have air injection holes at bottom ends
813
and
814
thereof. The polishing liquid supply apparatus
800
further includes an air supply source
815
for supplying air to top ends of the detection pipes
811
and
812
at certain pressures respectively, a differential pressure detector
818
for detecting a difference in the air pressure between the detection pipes
811
and
812
, and a control device
819
for controlling the opening angle of the control valve
807
. When the difference in the air pressure detected by the differential pressure detector
818
is larger than a set value
820
, the control device
819
increases the opening angle of the control valve
807
; and when the difference in the air pressure detected by the differential pressure detector
818
is smaller than a set value
820
, the control device
819
decreases the opening angle of the control valve
807
.
The concentration of the polishing liquid
2
in the polishing liquid tank
802
is controlled by adjusting, by controlling the control valve
807
, the amount of the additive liquid supplied to the mixer
801
based on the difference in the air pressure detected by the differential pressure detector
818
.
The chemical mechanical polishing system
700
shown in
FIG. 7
has the following problem. A portion for coupling the pipe
709
to the polishing liquid tank
701
and a portion for coupling the pipes
711
a
and
711
b
to the polishing liquid tank
701
do not have a structure for blocking the external air. Due to such a structure, a gas
703
contained in the polishing liquid tank
701
, which is adjusted to have an appropriate concentration to be used for polishing, is exposed to the external air. Accordingly, the external air invades into the polishing liquid tank
701
.
The polishing liquid supply apparatus
800
shown in
FIG. 8
has the following problem. External air invades into the polishing liquid tank
801
through the injection air holes at the bottom ends
813
and
814
of the detection pipes
811
and
812
.
The following problem occurs when these apparatuses are used to perform chemical mechanical polishing. When, for example, a polishing liquid containing cerium oxide (ceria) or the like as a polishing agent is used, the polishing liquid deteriorates the polishing characteristics thereof over time due to the change in pH thereof in the polishing liquid tank. Although it is possible to adjust the pH by adding and mixing more polishing liquid, it is difficult to improve the polishing characteristics once they are deteriorated.
In chemical mechanical polishing, a difference in the polishing rate of films of two or more different materials to be polished can be utilized. In such a case, when the pH of the polishing liquid is 7, which indicates the liquid is neutral, the pH of the liquid may sometimes exceed 7 over time. Then, the polishing rates of the films to be polished and the difference in the polishing rate are significantly changed. Thus, the obtained polishing characteristics are far from the desirable characteristics. For example, when a polishing liquid containing cerium oxide is used for polishing a film containing silicon oxide (SiO
2
) and silicon nitride (Si
3
N
4
) and the pH or the polishing liquid exceeds 7, a polishing rate
32
of an Si
3
N
4
film increases as shown in
FIG. 2
as well as a polishing rate
31
of an SiO
2
film, resulting in the Si
3
N
4
film being unnecessarily polished.
In order to avoid such an undesirable effect, the capacity of the polishing liquid tank needs to be restricted so as to prevent the polishing liquid
2
from staying in the polishing liquid tank for an extended period of time. When the used amount of the polishing liquid
2
is excessively small, the polishing liquid
2
needs to be disposed of long before the life expectancy of the polishing liquid
2
.
SUMMARY OF THE INVENTION
A polishing liquid supply apparatus according to the present invention for supplying a polishing liquid to a chemical mechanical polishing apparatus includes a polishing
Kamikubo Noritaka
Satoh Yuji
Banks Derris H.
Nixon & Vanderhye P.C.
Sharp Kabushiki Kaisha
LandOfFree
Polishing liquid supply apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polishing liquid supply apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polishing liquid supply apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2452347