Grinding machine

Details Grinding machine Grinding machine

2001-11-08

2004-02-03

Eley, Timothy V. (Department: 3723)

Abrading

Machine

Combined

C451S066000, C451S287000, C451S290000, C451S332000

Reexamination Certificate

active

06685542

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a grinding machine for use in grinding plate-like objects such as semiconductor wafers.
2. Related Art
Referring to
FIG. 7
, a plate-like object such as a semiconductor wafer W is attached to a chuck table
60
with its rear side up by using a protective tape T between its front side and the top surface of the chuck table
60
. The rear side of the semiconductor wafer W is ground by a grinding means
70
.
The grinding means
70
comprises a rotary spindle
71
, a mount
72
integrally connected to the rotary spindle
71
and a grinding wheel
73
fixed to the mount
72
. The annular grinding wheel
73
has pieces of grindstone
74
fixed to its lower surface, as seen from FIG.
8
. While the grinding wheel
73
is made to rotate, the grinding means
70
is lowered until the pieces of grindstone
74
have been applied to the rear side of the semiconductor wafer W under pressure, thereby grinding the rear surface of the semiconductor wafer W.
The semiconductor wafer W is coarse-ground until it has a predetermined thickness, and then the coarse-ground semiconductor wafer W is fine-ground so that it may have a smooth flat surface. The grinding machine is equipped with two grinding means
74
, which are provided with pieces of coarse- and fine-grindstone respectively.
Referring to
FIG. 9
, a turntable
80
has plural chuck tables (three chuck tables
83
,
84
and
85
in the drawing) rotatably supported thereon. By turning the turntable
80
about its center of rotation
80
a
, selected chuck tables are brought to and put below first and second grinding means
81
and
82
, which carry out coarse-grinding and fine-grinding, respectively. The chuck tables
83
,
84
and
85
can rotate about their pivots
83
a
,
84
a
and
85
a.
As seen from
FIG. 9
, the first grinding means
81
and the second grinding means
82
are so positioned relative to each other that the straight line L
1
passing through the center of rotation
81
a
of the first grinding means
81
and the center of rotation
84
a
of the chuck table
84
, which is put below the first grinding means
81
, may be parallel to the straight line L
2
passing through the center of rotation
82
a
of the second grinding means
82
and the center of rotation
85
a
of the chuck table
85
, which is put below the second grinding means
85
. The semiconductor wafer W fixedly held by the chuck table
84
is coarse-ground by the first grinding means
81
whereas the semiconductor wafer W fixedly held by the chuck table
85
is fine-ground by the second grinding means
82
.
Semiconductor wafers can be put in and taken out from the area at which the chuck table
83
is positioned. Thus, a finished semiconductor wafer can be removed from the chuck table when it is brought to the area, and an unfinished semiconductor wafer can be put on and fixedly attached to the chuck table while it is located there.
Referring to
FIG. 9
again, pieces of grindstone
93
set on an annular grinding wheel
92
of the second grinding means
82
pass through the center of rotation
85
a
of the chuck table
85
to rub against the semiconductor wafer W evenly while the chuck table
85
rotates about its center of rotation. Thus, a semiconductor wafer of predetermined thickness results.
Referring to
FIG. 10
, the chuck table
83
,
84
or
85
has a circular conical surface
83
b
,
84
b
or
85
b
formed on its top. For example, the chuck table is 200 mm in diameter, and the circular conical shape is 10 &mgr;m high at its center. Now, it is assumed that the rotary axis
84
a
of the chuck table
84
is so tilted by turning its adjustment screws
95
and
96
that the grinding plane
94
defined by the pieces of grindstone
93
of the second grinding means
82
may be parallel to the top surface
84
b
of the chuck table
84
radially at an annular sector area
91
at which a required fine-grinding is effected on the semiconductor wafer W, as seen from FIG.
11
.
When the chuck table
84
was positioned below the first grinding means
81
(see FIG.
9
), a grinding plane
88
defined by the pieces of grindstone
87
of the first grinding means
81
was not parallel to the top surface
84
b
of the chuck table
84
radially at an annular sector area
90
at which a required coarse-grinding was effected on the semiconductor wafer W, as seen from FIG.
12
.
As a result, the semiconductor wafer W was coarse-ground to be concave more or less, thus making its thickness uneven. Then, the concave wafer is subjected to the fine-grinding when the chuck table
84
is brought to and put below the second grinding means
82
. Even though the grinding plane
94
defined by the pieces of grindstone
93
of the second grinding means
82
is kept parallel to the top surface
84
b
of the chuck table
84
radially at the annular sector area
91
, the uneven thickness of the semiconductor wafer cannot be corrected, and therefore, the finished semiconductor wafer of uneven thickness results.
On the contrary, it is assumed that the rotary axis
84
a
of the chuck table
84
is so tilted that the grinding plane defined by the pieces of grindstone
88
of the first grinding means
81
may be parallel to the top surface
84
b
of the chuck table
84
radially at the annular sector area
90
at which a required coarse-grinding is effected on the semiconductor wafer W.
When the chuck table
84
is positioned below the second grinding means
82
, the grinding plane
94
of the second grinding means
82
is not parallel to the top surface
84
b
of the chuck table
84
radially at the annular sector area
91
at which a required fine-grinding is effected on the semiconductor wafer W. Accordingly, the precision with which the fine-grinding is effected is lowered. This is the same with the chuck table
83
or
85
.
SUMMARY OF THE INVENTION
In view of the above, one object of the present invention is to provide a grinding apparatus which is capable of effecting the coarse- and fine-grinding with precision.
To attain this object, a grinding machine comprises: at least a turn table; chuck tables for holding workpieces to be machined, the chuck tables being rotatably fixed to the turntable; a first grinding means for grinding the exposed surface of each work piece held on the chuck table; and a second grinding means for grinding the exposed and first-ground surface of each workpiece. The grinding machine is improved according to the present invention in that the first grinding means includes at least a first grinding wheel having pieces of grindstone so fixedly arranged as to define together a first grinding plane, a first spindle unit having a rotary spindle fixed to the first grinding wheel; the second grinding means includes at least a second grinding wheel having pieces of grindstone so fixedly arranged as to define together a second grinding plane and a second spindle unit having a rotary spindle fixed to the second grinding wheel, and the first and second grinding means are so arranged that the grinding area formed on the workpiece by the first grinding wheel at the time the workpiece is being ground by the first grinding wheel corresponds to the grinding area formed on the workpiece by the second grinding wheel at the time the workpiece is being ground by the second grinding wheel.
The first and second grinding means may be so arranged that a first angle formed between a linear line connecting from a center of rotation of the turntable to a center of rotation of a selected chuck table when the workpiece is being ground by the first grinding means and a linear line connecting from a center of the selected chuck table to a center of rotation of the rotary spindle of the first spindle unit when the workpiece is being ground by the first grinding means is equal to a second angle formed between a linear line connecting from the center of rotation of the turntable to the center of rotation of the selected chuck table when the work piece is being ground by the second grinding means and a linear lin

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