Abrading – Machine – Rotary tool
Reexamination Certificate
2000-02-04
2001-08-28
Eley, Timothy V. (Department: 3723)
Abrading
Machine
Rotary tool
C451S398000
Reexamination Certificate
active
06280306
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a wafer polishing apparatus and a wafer manufacturing method which are employed in a semiconductor production process for polishing surfaces of semiconductor wafers.
2. Description of the Related Art
Recently, with finer patterns resulting from an increased packing density of semiconductor devices, it has become more important to polish surfaces of semiconductor wafers as flat as possible during a production process so that, in particular, fine patterns of a multilayered structure can be easily and reliably formed. Under such situations, an attention has been focused on the chemical mechanical polishing (CMP) process which can provide a higher degree of flatness in polishing surface films.
The CMP process means a process for polishing and planarizing wafer surfaces in a chemical and mechanical manner with, e.g., a alkaline solution using SiO
2
as an abrasive, a neutral solution using SeO
2
, or an acidic solution using Al
2
O
3
. One example of wafer polishing apparatuses for implementing the CMP process is shown, by way of example, in FIG.
11
.
Referring to
FIG. 11
, a wafer polishing apparatus
100
comprises a wafer holding head
101
for holding a wafer W to be polished, and a polishing pad
102
bonded to an overall upper surface of a platen
103
in the form of a disk. The wafer holding head
101
is provided in plural number and is mounted to the underside of a carousel
104
which serves as a head driving mechanism. Each wafer holding head
101
is rotatably supported by a spindle
111
and is rotated on the polishing pad
102
in planetary fashion. Incidentally, the center position of the platen
103
and the center about which the wafer holding heads
101
revolve may be offset from each other.
The platen
103
is horizontally arranged at the center of a base
105
and is rotatable about its axis by a platen driving mechanism provided within the base
105
. Posts
107
are provided aside the base
105
, and an upper mount plate
109
for supporting a carousel driving mechanism
110
is disposed between the posts
107
. The carousel driving mechanism
110
has a function of rotating the carousel
104
, provided below the mechanism
110
, about its axis.
Abutment members
112
are disposed on the base
105
to project upward from the base
105
, and spacing adjusting mechanisms
113
are provided on respective upper ends of the abutment members
112
. Above the abutment members
112
, engagement members
114
are disposed in one-to-one relation. The engagement members
114
are fixed to the upper mount plate
109
and are projected downward from it. The abutment members
112
and the engagement members
114
are brought into contact with each other while the spacing adjusting mechanisms
113
are operated to adjust a distance between the wafer holding heads
101
and the polishing pad
102
to a proper one. The wafers W held on the wafer holding heads
101
are thereby brought into contact with the surface of the polishing pad
102
. The carousel
104
and the platen
103
are then rotated to polish the wafers W.
As shown in
FIG. 12
, the wafer holding heads
101
each comprise a head body
121
made up of a top plate
121
a and a tubular peripheral wall
121
b
fixed to an outer periphery of the top plate
121
a
; a diaphragm
122
made of an elastic material such as rubber and stretched inside the head body
121
; a disk-shaped carrier
123
fixed to a lower surface of the diaphragm
122
; an annular retainer ring
124
disposed between an outer periphery of the carrier
123
and the peripheral wall
121
b
in concentric relation with small gaps left relative to them; and a pressure regulating mechanism
125
for regulating a pressure in a fluid chamber
126
defined between the head body
121
and the diaphragm
122
.
The diaphragm
122
is held between the peripheral wall
121
b
and a diaphragm fixing ring
127
, and it is fixed to the head body
121
by screws
127
a
tightened into the peripheral wall
121
b
from above the diaphragm fixing ring
127
.
The carrier
123
is disposed on the lower side of the diaphragm
122
, and a carrier fixing ring
128
is disposed on the upper side of the diaphragm
122
with the diaphragm
122
held between the carrier
123
and the carrier fixing ring
128
. The carrier
123
is fixed to the diaphragm
122
by screws
128
a
tightened into the carrier
123
from above the carrier fixing ring
128
.
The retainer ring
124
in the annular form is fitted to a circular groove defined between the peripheral wall
121
b and the outer periphery of the carrier
123
such that the retainer ring
124
is positioned in concentric relation to the peripheral wall
121
b
and the carrier
123
while small gaps are left relative to both an inner surface of the peripheral wall
121
b
and an outer peripheral surface of the carrier
123
. Further, a retainer-ring fixing ring
129
is disposed on the upper side of the diaphragm
122
with the diaphragm
122
held between the retainer ring
124
and the retainer-ring fixing ring
129
. The retainer ring
124
is fixed to the diaphragm
122
by screws
129
a
tightened into the retainer ring
124
from above the retainer-ring fixing ring
129
. The retainer ring
124
is of a two-piece structure comprising a metal-made upper portion into which the screws
129
a
are tightened, and a resin-made lower portion which is brought into contact with the polishing pad
102
.
The wafer W is polished by the polishing apparatus including the above-described wafer holding head as follows. First, the wafer W is stuck to a wafer attraction sheet S, which is disposed on the underside of the carrier
123
, so as to locate in imbedded fashion within the retainer ring
124
. Then, the surface of the wafer W exposed to face downward is brought into contact with the polishing pad
102
bonded to the upper surface of the platen
103
, and is polished under rotation of the wafer holding head while a slurry containing a polishing abrasive is supplied.
In the above operation, the carrier
123
and the retainer ring
124
are supported by a floating structure such that they can independently displace in the vertical direction with elastic deformation of the diaphragm
122
. Therefore, pressing forces of the carrier
123
and the retainer ring
124
against the polishing pad
102
vary depending on the pressure in the fluid chamber
126
which is regulated by the pressure regulating mechanism
125
.
A lower end of the retainer ring
124
projects downward of the carrier
123
and holds an outer periphery of the wafer W stuck to the lower surface of the carrier
123
. This arrangement is intended not only to prevent the wafer W from dislodging from the carrier
123
during the polishing process, but also to prevent such a phenomenon that an outer peripheral area of the wafer W is polished in a larger amount than a central area thereof, by surrounding the wafer W with the retainer ring
124
and positioning a lower end surface of the retainer ring
124
at the same level as the lower surface (polished surface) of the wafer W.
In the above-described wafer polishing apparatus
100
in which the wafers W are polished by the polishing pad
102
with rotations of the wafer holding heads
101
and the platen
103
, uniform polishing of the wafers W is achieved by satisfying such a condition that a relative speed, at which the polished surface of the wafer W and the polishing pad
102
rotate while contacting with each other, is uniform in a plane (hereinafter referred to as an “in-plane speed uniform condition). Assuming that the angular speed of the wafer holding head
101
is Rh, the angular speed of the platen
103
is Rp, and the angular speed of the carousel
104
is Rc, the in-plane speed uniform condition is expressed by the following relation and is satisfied when the following relation holds:
Rp=Rh+Rc (1)
By polishing the wafer W under the above condition, the wafer W is uniformly polished when an apparatus
Hosoki Kanji
Iizuka Kazuo
Komasaki Masahito
Sano Jiro
Shibaya Hiroshi
Eley Timothy V.
Mitsubishi Materials Corporation
Nguyen Dung Van
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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