Abrading – Abrading process – With tool treating or forming
Reexamination Certificate
2001-08-10
2004-08-31
Eley, Timothy V. (Department: 3724)
Abrading
Abrading process
With tool treating or forming
C451S072000, C451S342000, C451S443000
Reexamination Certificate
active
06783441
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to an apparatus and a method for transferring a torque from a hub frame to a one-piece hub shaft and more particularly, relates to an apparatus and a method for transferring a torque from a rotating hub frame to a one-piece hub shaft without using connecting bolts between components of a hub shaft such that a possible breakage of the bolts and the resultant catastrophic failure of the apparatus can be avoided.
BACKGROUND OF THE INVENTION
Apparatus for polishing thin, flat semi-conductor wafers is well-known in the art. Such apparatus normally includes a polishing head which carries a membrane for engaging and forcing a semiconductor wafer against a wetted polishing surface, such as a polishing pad. Either the pad, or the polishing head is rotated and oscillates the wafer over the polishing surface. The polishing head is forced downwardly onto the polishing surface by a pressurized air system or, similar arrangement. The downward force pressing the polishing head against the polishing surface can be adjusted as desired. The polishing head is typically mounted on an elongated pivoting carrier arm, which can move the pressure head between several operative positions. In one operative position, the carrier arm positions a wafer mounted on the pressure head in contact with the polishing pad. In order to remove the wafer from contact with the polishing surface, the carrier arm is first pivoted upwardly to lift the pressure head and wafer from the polishing surface. The carrier arm is then pivoted laterally to move the pressure head and wafer carried by the pressure head to an auxiliary wafer processing station. The auxiliary processing station may include, for example, a station for cleaning the wafer and/or polishing head, a wafer unload station, or a wafer load station.
More recently, chemical-mechanical polishing (CMP) apparatus has been employed in combination with a pneumatically actuated polishing head. CMP apparatus is used primarily for polishing the front face or device side of a semiconductor wafer during the fabrication of semiconductor devices on the wafer. A wafer is “planarized” or smoothed one or more times during a fabrication process in order for the top surface of the wafer to be as flat as possible. A wafer is polished by being placed on a carrier and pressed face down onto a polishing pad covered with a slurry of colloidal silica or alumina in de-ionized water.
A schematic of a typical CMP apparatus is shown in
FIGS. 1A and 1B
. The apparatus
20
for chemical mechanical polishing consists of a rotating wafer holder
14
that holds the wafer
10
, the appropriate slurry
24
, and a polishing pad
12
which is normally mounted to a rotating table
26
by adhesive means. The polishing pad
12
is applied to the wafer surface
22
at a specific pressure. The chemical mechanical polishing method can be used to provide a planar surface on dielectric layers, on deep and shallow trenches that are filled with polysilicon or oxide, and on various metal films. CMP polishing results from a combination of chemical and mechanical effects. A possible mechanism for the CMP process involves the formation of a chemically altered layer at the surface of the material being polished. The layer is mechanically removed from the underlying bulk material. An altered layer is then regrown on the surface while the process is repeated again. For instance, in metal polishing a metal oxide may be formed and removed repeatedly.
A polishing pad is typically constructed in two layers overlying a platen with the resilient layer as the outer layer of the pad. The layers are typically made of polyurethane and may include a filler for controlling the dimensional stability of the layers. The polishing pad is usually several times the diameter of a wafer and the wafer is kept off-center on the pad to prevent polishing a non-planar surface onto the wafer. The wafer is also rotated to prevent polishing a taper into the wafer. Although the axis of rotation of the wafer and the axis of rotation of the pad are not collinear, the axes must be parallel.
The polishing pad is a consumable item used in a semiconductor wafer fabrication process. Under normal wafer fabrication conditions, the polishing pad is replaced after about 12 hours of usage. Polishing pads may be hard, incompressible pads or soft pads. For oxide polishing, hard and stiffer pads are generally used to achieve planarity. Softer pads are generally used in other polishing processes to achieve improved uniformity and smooth surface. The hard pads and the soft pads may also be combined in an arrangement of stacked pads for customized applications.
A problem frequently encountered in the use of polishing pads in oxide planarization is the rapid deterioration in oxide polishing rates with successive wafers. The cause for the deterioration is known as “pad glazing” wherein the surface of a polishing pad becomes smooth such that the pad no longer holds slurry in-between the fibers. This is a physical phenomenon on the pad surface not caused by any chemical reactions between the pad and the slurry.
To remedy the pad glazing effect, numerous techniques of pad conditioning or scrubbing have been proposed to regenerate and restore the pad surface and thereby, restoring the polishing rates of the pad. The pad conditioning techniques include the use of silicon carbide particles, diamond emery paper, blade or knife for scrapping the polishing pad surface. The goal of the conditioning process is to remove polishing debris from the pad surface, re-open the pores, and thus forms micro-scratches in the surface of the pad for improved life time. The pad conditioning process can be carried out either during a polishing process, i.e. known as concurrent conditioning, or after a polishing process.
A conventional conditioning disc for use in pad conditioning is shown in
FIG. 1C
in a perspective view of a CMP apparatus
50
. The apparatus
50
consists of a conditioning head
52
which includes a conditioning disc
68
mounted to a hub frame
70
, a polishing pad
56
, and a slurry delivery arm
54
positioned over the polishing pad. The conditioning head
52
is mounted on a conditioning arm
58
which is extended over the top of the polishing pad
56
for making sweeping motion across the entire surface of the pad. The slurry delivery arm
54
is equipped with slurry dispensing nozzles
62
which are used for dispensing a slurry solution on the top surface
60
of the polishing pad
56
. Surface grooves
64
are further provided in the top surface
60
to facilitate even distribution of the slurry solution and to help entrapping undesirable particles that are generated by coagulated slurry solution or any other foreign particles which have fallen on top of the polishing pad during a polishing process.
Inside the conditioning head
52
, is a hub shaft
72
integrally formed with a circular disc
74
at a lower end. This is shown in FIG.
2
. The hub shaft
72
, when assembled with a hub spacer
76
on a flat surface
78
on the shaft can be inserted into a hub frame
70
(shown in
FIG. 1
) for transferring a rotational torque from the hub frame
70
to a conditioning disc
68
(shown in FIG.
1
). The hub spacer
76
is fastened to the hub shaft
72
by two screws
82
and is equipped with a protruded pin
84
on a top surface
86
of the hub spacer
76
. The pin
84
is used to engage a recessed slot (not shown) provided in the hub frame
70
(shown in
FIG. 1
) such that the hub shaft
72
can be easily assembled or disassembled. Since the conditioning disc
68
which consists of the hub shaft
72
, the hub spacer
76
and the circular disc
74
operates in high torque during the pad conditioning process, the screws
82
that fasten the hub spacer
76
to the hub shaft
72
frequently break under such high torque operating conditions. When a failure, or breakage of the screws
82
occurs, the hub shaft
72
becomes loose from the hub frame
70
and causes a catastrophic failure of the conditionin
Chan Wen-Ten
Liang Yao Hsiang
Eley Timothy V.
Taiwan Semiconductor Manufacturing Co. Ltd.
Tung & Associates
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