Abrading – Precision device or process - or with condition responsive... – With indicating
Reexamination Certificate
1998-03-20
2001-02-06
Larson, Lowell A. (Department: 3725)
Abrading
Precision device or process - or with condition responsive...
With indicating
C451S005000, C451S006000, C451S057000, C451S287000, C451S288000
Reexamination Certificate
active
06183345
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a precision polishing apparatus and method for very precisely polishing a substrate, such as a semiconductor wafer or the like.
2. Description of the Related Art
Recently, as semiconductor devices tend to have ultrafine patterns and multilayer interconnections, precision polishing apparatuses for very precisely flattening the surfaces of semiconductor wafers of Si, GaAs, InP, SOI (silicon on insulator) or the like, are being demanded. Particularly, chemical mechanical polishing (CMP) apparatuses are known as precision polishing apparatuses for very precisely flattening the surfaces of substrates, such as wafers on which semiconductor devices are formed.
Conventional CMP apparatuses can be classified into two types as shown in
FIGS. 7 and 8
.
(1)
FIG. 7
is a schematic diagram illustrating an external appearance of a polishing processing unit of a CMP apparatus for performing polishing processing in a state in which the surface to be polished of a wafer
100
is downwardly placed.
As shown in
FIG. 7
, the wafer
100
is held in a state in which its surface to be polished is downwardly placed, and is polished by being pressed against a polishing pad
1011
having a diameter larger than the diameter of the wafer
100
while being rotated. While the wafer
100
is polished, an abrasive (slurry) is dripped onto the upper surface of the polishing pad
1011
.
In this type of apparatus, the wafer
100
is held by a wafer chuck
1003
, for example, by means of vacuum suction, bonding using wax, a solution or pure water. In order to prevent displacement of the wafer
100
, a guide ring
1004
is, in some cases, provided along the outer circumference of the wafer
100
. The diameter of the polishing pad
1011
on a table
1001
is 3-5 times the diameter of the wafer
100
. A suspension obtained by dispersing fine particles of silicon oxide in an aqueous solution of potassium hydroxide is used as the slurry.
(2) A method has also been proposed in which, as shown in
FIG. 8
, a wafer
100
is held on a wafer chuck
1103
having a guide ring
1104
and disposed on a wafer table
1101
, in a state in which the surface to be polished of the wafer
100
is upwardly placed, and the wafer
100
is polished using a polishing pad
1111
having a diameter smaller than the diameter of the wafer
100
.
These polishing apparatuses and methods can polish substrates, such as currently-used 8-inch semiconductor wafers or the like. Recently, however, as semiconductor integrated circuits tend to have fine patterns and adopt wafers having larger diameters, the diameters of wafers are expected to shift from 8 inches to 12 inches.
In order to polish large-diameter wafers, the conventional techniques have the following problems to be solved.
That is, in the apparatus shown in
FIG. 7
, the size of the polishing apparatus increases as the diameter of the wafer increases.
In the apparatus shown in
FIG. 8
, much time is required for uniformly polishing the entire surface of the wafer.
In the above-described conventional apparatuses, it is attempted to control the polishing property by optimizing the thickness, elasticity and the like of the polishing pad in order to polish an 8-inch wafer. In this case, however, it is difficult to assure fine adjustment and uniformity of the material of the polishing pad, and therefore, to very precisely polish a wafer having a larger diameter, such as 12 inches.
In particular, the polishing property of the polishing pad is degraded in the course of time. For example, while the life of the polishing pad is as long as hundreds of hours, the polishing property is degraded by tens of % within this time period.
In addition, flexibility is lacking of polishing a plurality of kinds of IC's (integrated circuits) having different chip sizes and different thicknesses and widths of interconnections with a high throughput.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a polishing apparatus and method having flexibility which can efficiently polish a large-area member to be polised to a desired shape.
According to one aspect, the present invention which achieves the above-described object relates to a polishing apparatus including a first polishing station which includes first holding means for holding a member to be polished in a state in which a surface to be polished thereof is upwardly placed, and a first polishing head for holding and rotating a polishing pad whose polishing surface is larger than the surface to be polished in a state of contacting the surface to be polished, a detection station for detecting a polished state of the surface to be polished in a state in which the surface to be polished is upwardly placed, and a second polishing station which includes second holding means for holding the member to be polished in a state in which the surface to be polished thereof is upwardly placed, and a second polishing head for holding and rotating a polishing pad whose polishing surface is smaller the the surface to be polished in a state of contacting the surface to be polished.
In one embodiment, the first polishing station, the detection station and the second polishing station are separated by partition means.
In another embodiment, the first polishing station is divided into a primary polishing station for performing polishing at a predetermined polishing speed, and a secondary polishing station for performing polishing at a speed lower than the polishing speed of the primary polishing station.
In still another embodiment, the apparatus further includes member-to-be-polished conveying means for conveying the member to be polished between the first polishing station, the detection station and the second polishing station in a state in which the surface to be polished of the member to be polished is upwardly placed.
In yet another embodiment, the first polishing station, the detection station and the second polishing station are provided within corresponding chambers separated by partition means and separated from atmospheric air.
In yet a further embodiment, the diameter of the polishing pad mounted on the first polishing head is smaller than twice the diameter of the surface to be polished.
According to another aspect, the present invention which achieves the above-described object relates to a polishing method including a first polishing step of mounting a member to be polished on first holding means in a state in which a surface to be polished of the member is upwardly placed, and polishing the surface to be polished by rotating a polishing pad whose polishing surface is larger than the surface to be polished in a state of contacting the surface to be polished, a detection step of detecting a polished state of the surface to be polished in a state in which the surface to be polished is upwardly placed, and a second polishing step of mounting the member to be polished on second holding means in a state in which the surface to be polished of the member is upwardly placed, and polishing the surface to be polished by rotating a polishing pad whose polishing surface is smaller than the surface to be polished in a state of contacting the surface to be polished.
In one embodiment, the first polishing step, the detection step and the second polishing step are separated by partition means.
In another embodiment, the first polishing step is divided into a primary polishing step of performing polishing at a predetermined polishing speed, and a secondary polishing step of performing polishing at a speed lower than the polishing speed of the primary polishing step.
In still another embodiment, the method further includes a conveying step of conveying the member to be polished between the first polishing step, the detection step and the second polishing step in a state in which the surface to be polished of the member to be polished is upwardly placed.
In yet another embodiment, the first polishing step, the detection step and the second polishing step are provided
Ikeda Osamu
Kamono Takashi
Nishimura Matsuomi
Ohta Satoshi
Takahashi Kazuo
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Hong William
Larson Lowell A.
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