Abrasive machine

Details Abrasive machine Abrasive machine

2000-02-15

2002-07-23

Rose, Robert A. (Department: 3723)

Abrading

Machine

Rotary tool

C451S388000

Reexamination Certificate

active

06422928

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to an abrasive machine, more precisely relates to an abrasive machine having: a holding section for holding a wafer on a lower face; an abrasive plate having an abrasive face for abrading the wafer; and a driving mechanism for relatively moving the abrading plate with respect to the wafer.
These days, semiconductor devices are highly integrated, so flatness of silicon wafers, which will be substrates of semiconductor devices, must be highly improved. To precisely abrade layers and wires on a wafer, the surface of the wafer must be highly flat. Thus, machines for abrading wafers are required to highly precisely abrade surfaces of wafers and layers, etc. formed on the surfaces thereof. Besides wafers of semiconductor devices, high accuracy of abrading wafer-shaped work pieces is required in other fields.
Some conventional abrading machines have air bags, which are provided to the holding sections so as to uniformly press whole wafer faces onto the abrasive faces.
An example of the holding section
55
is shown in FIG.
4
.
A head member
12
has a concave section
14
in a lower face thereof.
A holding plate
16
is provided in the concave section
14
of the head member
12
, and a lower face is a holding face for holding a wafer
20
.
A metallic bellows
56
is fixed between the holding plate
16
and the head member
12
. The metallic bellows
56
allows the holding plate
16
to move close to and away from and incline with respect to the lower face of the head member
12
. The metallic bellows
56
forms a pressure chamber
26
.
In the holding section
55
having the above described members, the pressure chamber
26
is pressurized by supplying a pressurized fluid from pressurizing means (not shown) so as to press the wafer
20
, with the holding plate
16
, onto the abrasive face
50
of the abrasive plate
52
.
The abrasive plate
52
is relatively moved with respect to the holding section
16
with the wafer
20
by a driving mechanism, so that the surface of the wafer
20
can be abraded by the abrasive face
50
.
By employing the metallic bellows
56
in the holding section
55
, the wafer
20
can be pressed onto the abrasive face
50
by pressing force, which is uniformly applied. And, the metallic bellows
56
can follow inclination and minute vertical movement of the abrasive face
50
, therefore abrading accuracy of the abrasive machine can be improved. Further, the metallic bellows
56
can stand against external force, which is applied sideward, by its own rigidity.
However, the metallic bellows
56
is made by piling a plurality of donut-shaped plates and mutually welding their inner edges and outer edges. Therefore, it is difficult to uniformly welding their edges, so the wafer
20
, which is held by the holding plate
16
, cannot be uniformly pressed onto the abrasive face
52
. And, the rigidity of the metallic bellows
56
is very high, so it cannot follow very minute change of pressure and motion. Further, the metallic bellows
56
causes liquation of metal ions, which must be avoided in the steps of manufacturing semiconductor devices.
To solve the above described disadvantages, as shown in
FIG. 5
, a holding section
60
includes an elastic member
62
, which is, for example, a rubber plate, being fixed between the holding plate
16
and the head member
12
so as to form a pressure chamber
26
, which allows the holding plate
16
to move close to and away from and incline with respect to a lower face of the head member
12
.
The holding section
60
will be explained with reference to FIG.
5
.
The abrasive plate
52
can be revolved on its own axis, and an abrasive cloth
51
is adhered on the abrasive plate
52
so as to form the abrasive face
50
. The holding section
60
, which is capable of revolving and vertically moving, is located above the abrasive face
50
. The holding section
60
includes: a head member
12
having a concave section, which is opened in a lower face thereof; a holding plate
16
having a lower face capable of holding the wafer
20
; the elastic member
62
, whose outer circumferential part
62
a
is fixed to an inner bottom face of the head member
12
and whose inner circumferential part
62
b
is fixed to an upper face of the holding plate
16
, suspending the holding plate
16
so as to allow very minute vertical and horizontal motion thereof; and the pressure chamber
26
being formed by dividing an inner space of the head member
12
with the holding plate
16
and the plate-shaped elastic member
62
. A fluid supplying means (not shown) is communicated to the pressure chamber
26
, so that pressurized fluid can be supplied into the pressure chamber
26
. An O-ring
64
is made of, for example, rubber. The O-ring
64
is provided between the outer circumferential face of the holding plate
16
and the inner circumferential face of the concave section
14
of the head member
12
, and it is capable of absorbing relative motion, e.g., rotation, swing motion, of the holding plate
16
with respect to the head member
12
.
In the conventional abrasive machine, the elastic member
62
, which is the rubber plate, makes the surface
20
a
of the wafer
20
, which is adhered on the holding plate
16
by water, quickly follow minute inclination and minute vertical movement of the abrasive face
50
as the air bag. Even if the surface
20
a
follows the abrasive face
50
, the whole surface
20
a
can be uniformly pressed onto the abrasive face
50
. With this action, the whole surface
20
a
can be highly uniformly abraded like a mirror. Further, the disadvantage of the liquation of the metal ions can be solved.
Note that, in the holding section
60
shown in
FIG. 6
, the wafer
20
is adhered onto the holding plate
16
by water, so a backing sheet, whose surface has high adsorptivity, is adhered on the surface of the holding plate
16
so as to securely adhere the wafer
20
thereonto.
However, in the conventional abrasive machine, the holding plate
16
is suspended by one plate-shaped elastic member
62
, so the whole surface of the holding plate cannot uniformly move, in the vertical direction, with enough stroke. Therefore, the holding plate
16
cannot fully follow the inclination and the vertical movement of the abrasive face
50
, so that the whole surface
20
a
of the wafer cannot be uniformly pressed onto the abrasive face
50
. Namely, the holding plate
16
does not have enough vertical stroke, so it can quickly follow the very minute movement of the abrasive face
50
but cannot follow when some conditions are changed. Especially, this disadvantage is serious in the case of precisely abrade large-sized wafers.
To solve this problem, using a rubber bellows instead of the elastic member
62
was proposed. But the elasticity of the rubber bellows is too high, so the rubber is irregularly deformed, and it is difficult to uniformly press the wafer
20
onto the abrasive face
50
. Then, a rubber bellows reinforced by piano wires, etc. was used, but the rubber bellows cannot uniformly move because of the reinforcing member, so it is difficult to quickly and uniformly press the wafer
20
onto the abrasive face
50
. It is also difficult to make the rubber bellows including the reinforcing members.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an abrasive machine, which is capable of solving the liquation of metal ions, making a holding plate, which holds a wafer on a lower face, quickly follow very minute movement of an abrasive face of an abrasive plate, uniformly pressing the whole surface of the wafer onto the abrasive face, and improving abrading accuracy.
To achieve the object, the abrasive machine of the present invention comprises:
an abrasive plate having an upper face, which is an abrasive face capable of abrading a wafer;
a holding section including:
a head member being located above the abrasive face with a prescribed separation;
a holding plate being provided between the head member and the abrasive face, the holding pl

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