U.S. patent application number 09/737006 was filed with the patent office on 2001-06-21 for abrasive machine.
This patent application is currently assigned to Fujikoshi Machinery Corp.. Invention is credited to Denda, Yasuhide, Furukawa, Masanori, Kuroiwa, Hisato, Nakamura, Yoshio.
Application Number | 20010003883 09/737006 |
Document ID | / |
Family ID | 18464516 |
Filed Date | 2001-06-21 |
United States Patent
Application |
20010003883 |
Kind Code |
A1 |
Denda, Yasuhide ; et
al. |
June 21, 2001 |
Abrasive machine
Abstract
The abrasive machine is capable of preventing deformation and
bad abrasion of an abrasive cloth, maintaining flatness of an
abrasive face of an abrasive plate and improving abrading accuracy.
The abrasive machine comprises the abrasive plate and a holding
unit for holding a work piece. In the holding unit, an inner head
has a first concave section. An outer head has a second concave
section. A holding plate is provided in the first concave section.
An elastic holding member forms a first chamber. An outer enclosing
member is provided to the outer head. An inner enclosing member is
provided between the outer enclosing member and the inner head. A
pressing member presses the abrasive face of the abrasive plate and
encloses the holding plate. An elastic ring member a second
chamber. A pressurizing unit pressurizes the chambers so as to
press the work piece and the pressing member onto the abrasive
face.
Inventors: |
Denda, Yasuhide;
(Nagano-shi, JP) ; Kuroiwa, Hisato; (Nagano-shi,
JP) ; Furukawa, Masanori; (Nagano-shi, JP) ;
Nakamura, Yoshio; (Nagano-shi, JP) |
Correspondence
Address: |
Jordan and Hamburg
122 East 42nd Street
New York
NY
10168
US
|
Assignee: |
Fujikoshi Machinery Corp.
|
Family ID: |
18464516 |
Appl. No.: |
09/737006 |
Filed: |
December 14, 2000 |
Current U.S.
Class: |
51/297 ;
257/E21.23; 451/286 |
Current CPC
Class: |
B24B 37/30 20130101;
H01L 21/30625 20130101 |
Class at
Publication: |
51/297 ;
451/286 |
International
Class: |
B24B 007/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 17, 1999 |
JP |
11-359440 |
Claims
What is claimed is:
1. An abrasive machine, comprising: a holding unit for holding a
work piece; and an abrasive plate having an abrasive face, which
abrades a surface of the work piece by relatively moving said
abrasive plate with respect to said holding unit, wherein said
holding unit includes: an inner head having a first concave
section, whose opening section is headed toward the abrasive face
of said abrasive plate; an outer head having a second concave
section, in which said inner head is provided and whose opening
section is headed toward the abrasive face of said abrasive plate,
a holding plate being provided in the first concave section and
having a holding face, on which the work piece is held; an elastic
holding member being fixed to said inner head and said holding
plate, allowing said holding plate to move with respect to said
inner head, and forming a first chamber for pressing the work piece
in the first concave section with said holding plate; an outer
enclosing member being provided to said outer head and enclosing
said inner head; an inner enclosing member being provided between
said outer enclosing member and said inner head and enclosing said
inner head; a pressing member for pressing the abrasive face of
said abrasive plate, said pressing member being formed into a ring
shape enclosing said holding plate; an elastic ring member being
fixed to said outer enclosing member and said inner enclosing
member, holding and allowing said pressing member to move with
respect to said outer head, and forming a second chamber in the
second concave section; and a pressurizing unit introducing
pressurized fluid into said first chamber and said second chamber
so as to press the work piece onto the abrasive face of said
abrasive plate with said holding plate and so as to press said
pressing member onto the abrasive face of said abrasive plate.
2. The abrasive machine according to claim 1, wherein the
pressurized fluid is introduce into said first chamber by a first
pressurizing unit, and the pressurized fluid is introduce into said
second chamber by a second pressurizing unit.
3. The abrasive machine according to claim 1, further comprising:
an inner head driving unit for rotating said inner head about a
shaft, which is arranged perpendicular to the surface of the work
piece, which has been held by said holding plate; and an outer head
driving unit for rotating said outer head about another shaft,
which is arranged perpendicular to the surface of the work piece,
which has been held by said holding plate.
4. The abrasive machine according to claim 3, wherein said inner
enclosing member is separable from said outer head, connected to
said outer head by said elastic ring member so as to be moved
together with said outer head, and rotatably held by said inner
head with a bearing.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an abrasive machine, more
precisely relates to an abrasive machine, which comprises a holding
unit for holding a work piece, e.g., a semiconductor wafer, and an
abrasive plate having an abrasive face, which abrades a surface of
the work piece by relatively moving the abrasive plate with respect
to the holding unit. For example, the abrasive face abrades a
surface of a semiconductor wafer, in which semiconductor chips are
formed, like a mirror face.
[0002] Recently, circuits in semiconductor devices are highly
integrated, so flatness and surface conditions of silicon wafers,
etc., which will be substrates of semiconductor devices, must be
highly improved. Further, insulating layers and cables paterns,
which are formed on the wafer so as to form the devices, are
abraded with higher flatness. Therefore, the abrasive machine must
abrade the surfaces of the wafers, like mirror faces, with higher
accuracy.
[0003] In a conventional abrasive machine, a whole surface of a
wafer is uniformly pressed onto an abrasive face of an abrasive
plate by an airbag of a wafer holding unit.
[0004] The wafer holding unit of the conventional abrasive machine
will be explained with reference to FIGS. 9 and 10.
[0005] In FIG. 9, an abrasive plate 50 is rotated about a vertical
shaft. An abrasive cloth 51 is adhered on an upper face of the
abrasive plate 50 so as to form an abrasive face 52. The wafer
holding unit 60 is provided above the abrasive plate 50. The wafer
holding unit 60 is rotated about a vertical shaft and moved in the
vertical direction.
[0006] The wafer holding unit 60 includes: a head 62 having a
concave section 62a, whose opening section is headed downward; a
wafer holding plate 64 having a holding face, on which the wafer 12
is held; an elastic member 66, whose outer edge 66b is fixed to an
enclosing section 62b of the head 62 and whose inner edge 66a is
fixed to an outer end section 64a of the wafer holding plate 64,
being formed like a plate and capable of allowing the wafer holding
plate 64 to move within a very small range; and an air-tightly
sealed chamber 65 being formed, in the head 62, by the wafer
holding plate 64 and the elastic member 66.
[0007] A vacuum unit 67 for sucking and holding the wafer 12 is
communicated to sucking holes 67a, which are opened in a bottom
face of the wafer holding plate 64, which acts as a wafer holding
face, via an air tube 67b. By actuating the vacuum unit 67, the
wafer 12 can be sucked and held on the wafer holding face of the
wafer holding plate 64.
[0008] A pressurizing unit 68 supplies pressurized fluid to the
chamber 65 so as to press the wafer 12 onto the abrasive face 52 of
the abrasive plate 50 together with the wafer holding plate 64.
[0009] A pressure reducing unit 69 reduces inner pressure of the
chamber 65.
[0010] A male tapered section 70, whose outer diameter is gradually
reduced downward, is downwardly projected from an inner ceiling
face of the head 62; a female tapered section 72, whose inner
diameter is gradually increased upward, is upwardly projected from
an upper face of the wafer holding plate 64. With this structure,
the male tapered section 70 fits in the female tapered section 72
when the pressure reducing unit 69 reduces the inner pressure of
the chamber 65.
[0011] In the conventional abrasive machine, the surface 12a of the
wafer 12 to be abraded is capable of quickly following inclination,
etc. of the abrasive face 52 because of the airbag function of the
elastic member 66, e.g., a rubber plate, so that the whole surface
12a of the wafer 12 can be uniformly pressed onto the abrasive face
52 even if the abrasive face 52 is inclined. With this action, the
whole surface 12a can be uniformly abraded or polished like a
mirror face.
[0012] By fitting the male tapered section 70 in the female tapered
section 72, the wafer holding plate 64 can be precisely positioned,
so that the wafer 12 can be positioned or adhered at a correct
position. Therefore, abrading accuracy and abrading efficiency can
be improved, and abrading steps can be executed automatically.
[0013] However, in the conventional abrasive machine, the surface
12a of the wafer 12 is pressed onto the abrasive face 52 of the
abrasive cloth 51, which is adhered on the abrasive plate 50, while
abrading or polishing the wafer 12. A part of the abrasive cloth
51, on which the wafer 12 is pressed, is slightly caved downward
with respect to other parts, so that a concave portion 51a (see
FIG. 10) is formed. And, a lower outer edge 12b of the wafer 12
contacts an inner face of the concave portion 51a and is abraded
thereby.
[0014] If the lower outer edge 12b of the wafer 12 is abraded by
the inner face of the concave portion 51a of the abrasive cloth 51,
the abrasive face 52 is waved and badly abraded, so that flatness
of the abraded surface 12a of the wafer 12 is made lower.
[0015] The abrasive face 52 of the abrasive cloth 51, which has
been waved and badly abraded, can be recovered by recovering means.
In the conventional abrasive machine, for example, the recovering
means, e.g., a dummy wafer, a ceramic plate, is attached to the
wafer holding plate 64 of the holding unit 60, then the recovering
means is pressed onto the abrasive face 52 so as to recover the
damaged abrasive face 52. In the case of a new abrasive cloth 51, a
surface condition of the new abrasive cloth 51 is uniformed by the
recovering member.
[0016] The step of recovering the abrasive cloth 51 cannot be
simultaneously executed with the abrasive step. If the recovering
step is executed before or after the abrasive step, required time
of the abrasive step and the recovering step must be longer and
working efficiency cannot be improved.
[0017] Conditions, e.g., pressing force, rotational speed of the
wafer holding plate 64, in the abrasive step are different from
those in the recovering step, but the wafer holding plate 64 is
used in the both steps. Therefore, the rotational speed of the
wafer holding plate 64 and the pressing force applied to the wafer
holding plate 64 (the inner pressure of the chamber 65) must be
newly set when the abrasive step or the recovering step is
executed. The change of the conditions is troublesome, so that
working efficiency and manufacturing efficiency cannot be
improved.
SUMMARY OF THE INVENTION
[0018] An object of the present invention is to provide an abrasive
machine, which is capable of preventing deformation and bad
abrasion of the abrasive cloth, maintaining flatness of the
abrasive face of the abrasive plate and improving abrading
accuracy.
[0019] To achieve the object, the abrasive machine of the present
invention comprises:
[0020] a holding unit for holding a work piece; and
[0021] an abrasive plate having an abrasive face, which abrades a
surface of the work piece by relatively moving the abrasive plate
with respect to the holding unit,
[0022] wherein the holding unit includes:
[0023] an inner head having a first concave section, whose opening
section is headed toward the abrasive face of the abrasive
plate;
[0024] an outer head having a second concave section, in which the
inner head is provided and whose opening section is headed toward
the abrasive face of the abrasive plate,
[0025] a holding plate being provided in the first concave section
and having a holding face, on which the work piece is held;
[0026] an elastic holding member being fixed to the inner head and
the holding plate, allowing the holding plate to move with respect
to the inner head, and forming a first chamber for pressing the
work piece in the first concave section with the holding plate;
[0027] an outer enclosing member being provided to the outer head
and enclosing the inner head;
[0028] an inner enclosing member being provided between the outer
enclosing member and the inner head and enclosing the inner
head;
[0029] a pressing member for pressing the abrasive face of the
abrasive plate, the pressing member being formed into a ring shape
enclosing the holding plate;
[0030] an elastic ring member being fixed to the outer enclosing
member and the inner enclosing member, holding and allowing the
pressing member to move with respect to the outer head, and forming
a second chamber in the second concave section; and
[0031] a pressurizing unit introducing pressurized fluid into the
first chamber and the second chamber so as to press the work piece
onto the abrasive face of the abrasive plate with the holding plate
and so as to press the pressing member onto the abrasive face of
the abrasive plate.
[0032] In the abrasive machine of the present invention, the
pressurized fluid is introduced into the first chamber of the inner
head, so that the work piece, which has been held by the holding
plate, can be pressed onto the abrasive face of the abrasive plate.
Further, the pressing member can be pressed onto the abrasive face
of the abrasive plate by pressurizing the second chamber. With this
action, the pressing member can be pressed onto the abrasive face
of the abrasive plate while the surface of the work piece is
abraded, so that flatness of the abrasive face can be maintained,
and working efficiency and abrading accuracy of the abrasive
machine can be improved.
[0033] In the abrasive machine, the pressurized fluid may be
introduce into the first chamber by a first pressurizing unit, and
the pressurized fluid may be introduce into the second chamber by a
second pressurizing unit. With this structure, the pressing member
can be pressed onto the abrasive face of the abrasive cloth with
pressing force corresponding to pressing force for pressing the
work piece onto the abrasive face. Therefore, the work piece can be
abraded with higher abrading accuracy.
[0034] The abrasive machine may further comprise:
[0035] an inner head driving unit for rotating the inner head about
a shaft, which is arranged perpendicular to the surface of the work
piece, which has been held by said holding plate; and
[0036] an outer head driving unit for rotating the outer head about
another shaft, which is arranged perpendicular to the surface of
the work piece, which has been held by said holding plate. With
this structure, rotaitonal speed of the work piece and the pressing
member can be separately and properly controlled, so that the
abrading accuracy can be improved.
[0037] In this abrasive machine, the inner enclosing member may be
separable from the outer head, connected to the outer head by the
elastic ring member so as to be moved together with the outer head,
and rotatably held by the inner head with a bearing. With this
structure, the inner head and the outer head including the inner
enclosing member can be separately rotated and properly
positioned.
BRIEF DESCRIPTION OF THE INVENTION
[0038] Embodiments of the present invention will now be described
by way of examples and with reference to the accompanying drawings,
in which:
[0039] FIG. 1 is a sectional view of a holding unit of the abrasive
machine of a first embodiment of the present invention;
[0040] FIG. 2 is a sectional view of the holding unit of the first
embodiment wherein compressed air is introduced thereinto;
[0041] FIG. 3 is an explanation view showing a state in which an
abrasive face of an abrasive cloth, which is employed in the
abrasive machine shown in FIGS. 1 and 2, is pressed by a pressing
member;
[0042] FIG. 4 is a bottom view of a bottom face of a pressing
member, which contacts an abrasive cloth;
[0043] FIG. 5 is a driving mechanism of the abrasive machine of the
first embodiment;
[0044] FIG. 6 is a sectional view of the holding unit of the
abrasive machine of a second embodiment;
[0045] FIG. 7 is a sectional view of the holding unit of the second
embodiment wherein the compressed air is introduced thereinto;
[0046] FIG. 8 is a sectional view of the holding unit of the
abrasive machine of a third embodiment;
[0047] FIG. 9 is a sectional view of the wafer holding unit of the
conventional abrasive machine; and
[0048] FIG. 10 is an explanation view showing the state in which
the abrasive face of the abrasive cloth, which is employed in the
conventional abrasive machine shown in FIG. 9 is pressed by the
wafer.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0049] Preferred embodiments of the present invention will now be
described in detail with reference to the accompanying
drawings.
First Embodiment
[0050] FIG. 1 is a sectional view of a holding unit of the abrasive
machine of a first embodiment; FIG. 2 is a sectional view of the
holding unit of, in which compressed air is introduced into the
holding unit; FIG. 3 is an explanation view showing a state in
which an abrasive face of an abrasive cloth is pressed by a
pressing member; FIG. 4 is a bottom view of a bottom face of a
pressing member, which contacts an abrasive cloth; and FIG. 5 is a
driving mechanism of the abrasive machine.
[0051] In the first embodiment, the abrasive machine abrades or
polishes a surface of a silicon wafer (a work piece). The abrasive
machine comprises a holding unit 10 for holding the wafer 12 and an
abrasive plate 50 having an abrasive face 52, which abrades the
surface 12a of the wafer 12 by relatively moving the abrasive plate
50 with respect to the holding unit 10. The surface 12a of the
wafer 12 can be polished like a mirror face.
[0052] The holding unit 10 includes: an inner head 20 having a
first concave section 21, whose opening section is headed toward
the abrasive face 52 of the abrasive plate 50; and an outer head 30
having a second concave section 31, in which the inner head 20 is
provided and whose opening section is also headed toward the
abrasive face 52 of the abrasive plate 50.
[0053] The inner head 20 includes: a wafer holding plate (a holding
plate) 22 being provided in the first concave section 21 and having
a holding face 22a, on which the wafer 12 is held; and an elastic
holding member 24 being fixed to the inner head 20 and the holding
plate 22, allowing the holding plate 22 to move, in the vertical
direction, etc., with respect to the inner head 20 and forming a
first chamber 25 for pressing the wafer 12 in the first concave
section 21 with the holding plate 22.
[0054] Details of the inner head 20 and peripheral elements will be
explained.
[0055] The inner head 20 constitutes a base portion of the holding
unit 10, which holds the wafer 12. As described above, the inner
head 20 has the first concave section 21, whose opening section is
headed downward.
[0056] A bottom face 22a of the holding plate 22 holds the wafer 12
as a holding face. The holding plate 22 is provided in the inner
head 20 and enclosed by an outer edge section 20a. The holding face
22a is located under a bottom face of the outer edge section
20a.
[0057] In the first embodiment, the wafer 12 is adhered onto the
holding face 22a of the holding plate 22 by water. A bucking member
(not shown) is adhered on the holding face 22a. The bucking member
has highly adsorptive surface, so that the wafer 12 can be securely
adhered thereon by surface tension and viscosity of a liquid, e.g.,
water.
[0058] In the case of adhering the wafer 12 onto the holding face
22a by water, a ring-shaped template (not shown), which is capable
of enclosing the wafer 12, is attached on the holding face 22a so
as to prevent the wafer 12 from sliding sideward. An inner diameter
of the template is 1 mm or less, e.g., 0.3 mm, greater than an
outer diameter of the wafer 12. In the present embodiment, the
outer diameter of the wafer 12 is about 300 mm. As described above,
the difference between the inner diameter of the template and the
outer diameter of the wafer 12 is very small with respect to the
outer diameter of the wafer 12. Thickness of the template is
thinner than that of the wafer 12.
[0059] Sliding the wafer 12 on the holding face 22a can be
prevented by other means other than the template. For example, an
outer diameter of the holding face 22a is made equal to that of the
wafer 12, and the sliding action of the wafer 12 may be prevented
by a ring-shaped pressing member 36. By using the pressing member
36, over-abrasion of an outer edge 12b (see FIG. 10) of the wafer
12 can be prevented. Namely, the pressing member 36 presses the
abrasive cloth 51 in the vicinity of the outer edge 12b of the
wafer 12, so that the abrasive cloth 51 enclosing the outer edge
12b of the wafer 12 is pressed downward. With this action, friction
between the outer edge 12b of the wafer 12 and the abrasive cloth
51 is made smaller, so that the over-abrasion can be prevented.
[0060] The elastic holding member 24 is made of an elastic material
and formed into a plate. In the present embodiment, the elastic
holding member 24 is made of a donut-shaped hard rubber, e.g.,
nitrile rubber including cloth.
[0061] An outer edge 24b of the elastic holding member 24 is fixed
to the outer edge section 20a of the inner head 20; an inner edge
24a of the elastic holding member 24 is fixed to an upper face of
an outer edge of the holding plate 22. Namely, the outer edge 24b
of the elastic holding member 24 is vertically clamped by members
constituting the outer edge section 20a of the inner head 20 and
fixed by bolts (not shown). On the other hand, the inner edge 24a
of the elastic holding member 24 is vertically clamped by the
holding plate 22 and a press member 23 and fixed by bolts (not
shown).
[0062] With this structure, the elastic holding member 24 holds and
allows the holding plate 22 to move, in the horizontal and vertical
directions, with respect to the inner head 20.
[0063] The first chamber 25 for pressing the wafer 12 is formed in
the inner head 20 by the holding plate 22 and the elastic holding
member 24. Pressurized fluid, e.g., compressed air, is introduced
into the first chamber 25 by a pressurizing unit 28. By increasing
inner pressure of the first chamber 25 by the pressurizing unit 28,
the wafer 12 can be pressed onto the abrasive face 52 of the
abrasive plate 50 with the holding plate 22, so that the surface
12a of the wafer 12 can be abraded or polished properly.
[0064] Note that, the pressurizing unit 28 has a pressure regulator
(not shown) for adjusting the inner pressure of the first chamber
25.
[0065] The outer head 30 includes: an outer enclosing member 30a
enclosing the inner head 20; and an inner enclosing member 33 being
provided between the outer enclosing member 30a and the inner head
20 and enclosing the inner head 20; the pressing member 36, whose
sectional shape is an L-shape, being formed into a ring shape
enclosing the holding plate 22 and pressing the abrasive face 52 of
the abrasive plate 50; and an elastic ring member 34 being fixed to
the outer enclosing member 30a and the inner enclosing member 33,
holding and allowing the pressing member 36 to move, in the
vertical and horizontal directions, with respect to the outer head
30, and forming a second chamber 35 in the outer head 30.
[0066] Next, details of the outer head 30 will be explained.
[0067] The outer head 30 constitutes an outer base part of the
holding unit 10, which holds the wafer 12. An upper section 30b,
which is formed like a disk, and the ring-shaped outer enclosing
member 30a are integrally connected in the outer head 30. The
second concave section 31, whose opening section is headed
downward, is formed inside of the inner enclosing member 33.
[0068] In the present embodiment, the inner enclosing member 33 is
detachably attached to the outer head 30, and the elastic ring
member 34 connects the inner enclosing member 34 to the outer head
30. With this structure, the inner enclosing member 33 is moved
together with the outer head 30. Further, the inner enclosing
member 33 is rotatably held by the inner head 20 with a bearing
40.
[0069] The inner enclosing member 33 is formed like an inverted
bowl, and a through-hole is formed a center part thereof. A seal
ring 41 is fitted to an inner edge of the inner enclosing member 33
so as to air-tightly seal a gap between the inner head 20 and the
inner enclosing member 33, so that the second chamber 35 can be
air-tightly sealed.
[0070] By employing the bearing 40 and the seal ring 41, the second
chamber 35 can be air-tightly sealed, and the inner head 20 and the
outer head 30, which includes the inner enclosing member 33, can be
independently rotated.
[0071] The elastic ring member 34 is made of an elastic material
and formed into a ring plate. In the present embodiment, the
elastic ring member 34 is made of a donut-shaped hard rubber, e.g.,
nitrile rubber including cloth.
[0072] An outer edge 34b of the elastic ring member 34 is fixed to
the outer enclosing member 30a of the outer head 30; an inner edge
34a of the elastic ring member 34 is fixed to the inner enclosing
member 33, which is rotated together with the outer head 30.
Namely, the outer edge 34b of the elastic ring member 34 is
vertically clamped by members constituting the outer enclosing
member 30a and fixed by bolts (not shown). On the other hand, the
inner edge 34a of the elastic ring member 34 is vertically clamped
by members constituting the inner enclosing member 33 and fixed by
bolts (not shown). The pressing member 36, whose pressing face is
headed toward the abrasive face 52 of the abrasive plate 50, is
fixed to the elastic ring member 34.
[0073] With this structure, the elastic ring member 34 holds and
allows the pressing member 36 to move, in the horizontal and
vertical directions, with respect to the inner head 20.
[0074] The second chamber 35 for pressing the pressing member 36 is
formed in the outer head 30 by the elastic ring member 34. The
pressurized fluid, e.g., compressed air, is introduced into the
second chamber 35 by the pressurizing unit 28. By increasing inner
pressure of the second chamber 35 by the pressurizing unit 28, the
pressing member 36 can be pressed onto the abrasive face 52 of the
abrasive plate 50, so that the abrasive face 52 of the abrasive
plate 50 can be properly pressed. Details of this action will be
explained later.
[0075] Note that, the pressurizing unit 28 supplies the compressed
air to the first and the second chambers 25 and 35. Namely, as
shown in FIG. 2, the compressed air is supplied via an air path
27a. Then, the compressed air is introduced into the first chamber
25 and simultaneously introduced into the second chamber 35 via
through-holes 26 of an upper section 20b of the inner head 20. In
FIG. 2, spaces filled with the compressed air are indicated by
hatching. With this structure, the wafer 12 and the pressing member
can be simultaneously pressed onto the abrasive face 52.
[0076] The action of the pressing member 36 will be explained with
reference to FIG. 3, which shows the state in which the pressing
member 36 is pressed on the abrasive cloth 51. The compressed air,
which has been introduced into the first chamber 25, presses the
surface 12a of the wafer 12 on the abrasive face 52 of the abrasive
cloth 51 with a predetermined force. Simultaneously, the compressed
air, which has been introduced into the second chamber 35, presses
the bottom face of the pressing member 36, which is parallel to the
abrasive face 51, on the abrasive face 52 of the abrasive cloth 51.
By pressing the pressing member 36 on the abrasive face 52, a part
of the abrasive cloth 51, which corresponds to the bottom face of
the pressing member 36 and encloses the lower outer edge 12b (see
FIG. 10) of the wafer 12, is pressed downward. In the conventional
abrasive machine, as shown in FIG. 10, the lower outer edge 12b of
the wafer 12 contacts the inner face of the concave portion 51a and
the contact part of the abrasive cloth 51 is concentratedly
damaged, so that the abrasive face 52 is waved and badly abraded.
On the other hand, in the first embodiment, friction is not
concentrated to the lower outer edge 12b of the wafer 12 (see FIG.
3), so that the abrasive cloth 51 is not concentratedly damaged and
waving and bad abrasion of the abrasive cloth 51 can be prevented.
Further, number of recovering the abrasive cloth 51 can be
reduced.
[0077] The pressing member 36 is, for example, a ring-shaped metal
disk or a net-shaped disk. Further, diamond grains may be included
in the bottom face of the pressing member 36, and the bottom face
may be coated with diamond CVD film. If the pressing member 36 is
made of a deposited grind stone or a ceramic having a properly
rough surface, the abrasive face 52 of the abrasive plate 50 can be
efficiently dressed. Thus, a dressing member may be used as the
pressing member 36.
[0078] The pressing member 36 of the present embodiment is formed
into a ring shape and fixed to the elastic ring member 34. To
properly fixed to the elastic ring member 34, the pressing member
36 has a thicker section 36a. The elastic ring member 34 is clamped
by the thicker section 36a and a ring member 36b, and the bolts
(not shown) integrates them, so that the pressing member 36 can be
fixed to the elastic ring member 34.
[0079] The pressing face 36c (the bottom face) of the pressing
member 36 is inwardly extended from a lower end of the thicker
section 36a. An inner edge of the pressing face 36c is extended
close to an outer edge of the holding plate 22. The pressing member
36 is extended and covers bottom faces of the inner enclosing
member 33 and the outer edge section 20a. With this structure, the
pressing face 36c of the pressing member 36 is efficiently
located.
[0080] If the pressing member 36 wholly encloses an outer
circumferential edge of the wafer 12, it is difficult to supply
slurry for abrading the wafer 12 onto the abrasive face 52 of the
abrasive cloth 51.
[0081] To overcome this disadvantage, guide grooves 36d, which
introduce the slurry onto the abrasive face 51, are formed in the
bottom face of the pressing member 36 as shown in FIG. 4.
[0082] The guide grooves 36d are curved in directions corresponding
to the rotational direction "R" of the pressing member 36. With
this structure, the slurry can be properly introduced into the
inner space of the pressing member 36 via the guide grooves 36d.
One of flowing directions of the slurry is shown as an arrow "S". A
sectional shape of the guide groove 36d may be a V-shape, a
U-shape, etc.
[0083] Forming the guide grooves 36d is effective in the case of
employing the large abrasive plate 50, whose diameter is much
greater than that of the wafer 12. On the other hand, in the case
of employing the abrasive plate 50, whose diameter is equal to or
slightly greater than that of the wafer 12, through-holes may be
formed in the abrasive plate 50 and the abrasive cloth 51 so as to
supply the slurry onto the abrasive face 52, via the through-holes,
from a lower side. In the case of the small abrasive plate 50, it
is difficult to effectively supply the slurry, from outside, to the
whole surface 12a of the wafer 12.
[0084] By the pressing member 36, abrading the wafer 12 and
pressing the abrasive face 52 of the abrasive plate 50 can be
executed simultaneously, so that the deformation and the bad
abrasion of the abrasive face 52 can be prevented. Therefore,
working efficiency can be improved, and wafers can be always
abraded, by the good abrasive face 52, with higher abrading or
polishing accuracy.
[0085] If the dressing member is used for pressing the abrasive
face 52 and the dressing step is separately executed from the
abrading step, frequency of executing the dressing step can be
reduced, so that working and manufacturing efficiency can be
improved.
[0086] A rotational driving mechanism and an vertical driving
mechanism of the innr head 20 and the outer head 30 will be
explained.
[0087] An inner bearing 42 is provided between an outer
circumferential face of an inner shaft 27, which is integrated with
the inner head 20, and an inner circumferential face of an outer
shaft 37, which is integrated with the outer head 30. With this
structure, the inner head 20 and the outer head 30 can be rotated
at different speed.
[0088] An inner seal ring 43 air-tightly seals a gap between the
outer circumferential face of the inner shaft 27 and the inner
circumferential face of the outer shaft 37.
[0089] An inner head driving unit 44 rotates the inner head 20
about a shaft, which is provided to the holding plate 22 and
arranged perpendicular to the surface 12a of the wafer 12, which
has been held by the holding plate 22.
[0090] As shown in FIG. 5, a motor 45 rotates the inner head 20. A
pinion gear 45a is fixed to an output shaft of the motor 45.
[0091] A driven gear 46 is fixed to an upper end of the inner shaft
27 and engaged with the pinion gear 45a.
[0092] An upper bearing 47 allows the inner shaft 27 to smoothly
rotate with respect to the outer shaft 37.
[0093] With this structure, the inner shaft 20, which is fixed to a
lower end of the long inner shaft 27, can be rotated by the motor
45. And the wafer 12, which has been held by the holding plate 22,
can be rotated about an axis, which is perpendicular to the surface
12a of the wafer 12, together with the inner head 20.
[0094] An outer head driving unit 54 rotates the outer head 30
about a shaft, which is provided to the holding plate 22 and
arranged perpendicular to the surface 12a of the wafer 12, which
has been held by the holding plate 22.
[0095] As shown in FIG. 5, a motor 55 rotates the outer head 30. A
pinion gear545a is fixed to an output shaft of the motor 55.
[0096] A driven gear 56 is fixed to the outer shaft 37 and engaged
with the pinion gear 55a.
[0097] Bearings 58 are vertically arranged and allow the outer
shaft 37 to smoothly rotate with respect to a base 14.
[0098] With this structure, the outer shaft 30, which is fixed to a
lower end of the long outer shaft 37, can be rotated by the motor
55. And the pressing member 36, which has been connected to the
outer head 30 by the elastic ring member 34, can be rotated about
an axis, which is perpendicular to the surface 12a of the wafer 12,
together with the outer head 30.
[0099] Since the inner head driving unit 44 and the outer head
driving unit 54 are separately provided, rotational speed of the
wafer 12 and the pressing member 36 can be separately and properly
controlled, so that abrading conditions can be properly defined and
the abrading accuracy can be improved.
[0100] In FIG. 5, a cylinder unit 74 vertically moves a head
section, which includes the inner head 20, the inner shaft 27 and
the outer shaft 37.
[0101] A rear end 74a of the cylinder unit 74 is fixed to the base
14; a front end of a cylinder rod 74b of the cylinder unit 74 is
fixed to an elevating member 76 with a connector 75.
[0102] Note that, the motor 45 for rotating the inner head 20 is
fixed on the elevating member 76.
[0103] The outer shaft 37 is not vertically moved with respect to
the elevating member 76. But the outer shaft 37 is rotatably held
by a bearing 77, which is capable of receiving load in the thrust
direction.
[0104] A stopper 79 is provided to the upper end of the inner shaft
27, so that the inner shaft 27 is not vertically moved with respect
to the outer shaft 37. But the inner shaft 27 is rotatably held by
the bearings 42 and 47. With this structure, the inner shaft 27 is
also rotatably held by the elevating member 76 so as not to fall
down.
[0105] A cylindrical section 14a is upwardly extended from the base
14. The outer shaft 37 is pierced through the cylindrical section
14a. The outer shaft 37 is vertically moved and rotated therein. An
inner cylindrical member 78 is integrated with the outer shaft 37
by a key 16, so that the inner cylindrical member 78 can be rotated
together with the outer shaft 37. The driven gear 56 covers the
inner cylindrical member 78 and is fixed thereto. The pinion gear
55a of the motor 55 is engaged with the driven gear 56. Note that,
the motor 55 for rotating the outer head 30 is fixed on the base
14.
[0106] By driving the motor 55, the outer head 30 is rotated
together with the outer shaft 37. Further, by driving the cylinder
unit 74, the outer shaft 37 is slid in the inner cylindrical member
78, so that the head section can be moved in the vertical
direction.
[0107] As described above, the driving mechanism constitutes: means
for vertically moving the wafer 12 so as to make the surface 12a of
the wafer 12 contact the abrasive face 52 of the abrasive plate 50;
means for rotating the wafer 12 about its own axis; and means for
rotating the pressing member 37 about its own axis.
[0108] An inlet 29 is provided to the upper end of the inner shaft
27 and communicated to the pressurizing unit 28. The inlet 29 is
also communicated to the air path 27a, which is formed in the inner
shaft 27 and communicated to the first chamber 25. Note that, in
the present embodiment, the pressurizing unit 28 is a
compressor.
[0109] A distributor (not shown) may be provided to the inlet 29 so
as to prevent a twist of air tubes, which is occurred by the
rotation.
[0110] Further, the abrasive machine has a slurry feeding unit (not
shown).
Second Embodiment
[0111] A second embodiment will be explained with reference to
FIGS. 6 and 7. The elements explained in the first embodiment are
assigned the same symbols and explanation will be omitted.
[0112] FIG. 6 is a sectional view of the holding unit of the
abrasive machine of the second embodiment. And, FIG. 7 is a
sectional view of the holding unit of the second embodiment wherein
the compressed air is introduced thereinto.
[0113] Features of the second embodiment are a first pressurizing
unit 38, which introduces the pressurized fluid into the first
chamber 25 so as to press the surface 12a of the wafer 12, which
has been held by the holding plate 22, onto the abrasive face 52 of
the abrasive plate 50; and a second pressurizing unit, which
introduces the pressurized fluid into the second chamber 35 so as
to press the pressing member 36 onto the abrasive face 52 of the
abrasive plate 50. Namely, two pressurizing units 38 and 39 are
separately provided. An inlet 39a, to which the pressurized fluid,
e.g., compressed air, is supplied from the second pressurizing unit
39 so as to pressurize the second chamber 35, is provided to an
upper face 30b of the outer head 30. Unlike the first embodiment,
no through-holes 26 (see FIG. 1) are not formed.
[0114] In the second embodiment, spaces including the first chamber
25 are filled with the compressed air from the first pressurizing
unit 38 and indicated by parallel-hatching; spaces including the
second chamber 35 are filled with the compressed air from the
second pressurizing unit 39 and indicated by cross-hatching (see
FIG. 7).
[0115] Pressure of the compressed air supplied into the first
chamber 25 can be different from pressure of the compressed air
supplied into the second chamber 35. Namely, the force pressing the
wafer 12 and the force for pressing the pressing member 36 can be
controlled separately. With this structure, the pressing member 36
can be pressed onto the abrasive face 52 of the abrasive cloth 51
with the pressing force corresponding to the force for pressing the
wafer 12 onto the abrasive face 52. Therefore, the wafer 12 can be
abraded with higher abrading accuracy.
[0116] Note that, if a pressure regulator (not shown), which
adjusts the pressure in the first chamber 25, and a pressure
reduction regulator (not shown), which adjust the pressure in the
second chamber 35, are provided, the pressure in the first and the
second chambers 25 and 35 can be separately controlled even if the
compressed air is supplied from a common source.
[0117] If a pressure reducing unit (not shown) is communicated to
the first chamber 25, the holding plate 22 can be drawn upward
while the pressure reducing unit is driven. With this structure,
only the pressing member 36, which is held by the elastic ring
member 34, can be pressed onto the abrasive face 52 by driving the
second pressurizing unit 39. In this case, if the dressing member
is employed as the pressing member 36, the abrasive face 52 can be
dressed by the dressing member.
[0118] If a pressure reducing unit (not shown) is communicated to
the second chamber 35, the pressing member 36, which is held by the
elastic ring member 34, can be drawn upward while the pressure
reducing unit is driven. With this structure, only the wafer 12,
which is held by the holding plate 22, can be pressed onto the
abrasive face 52 by driving the first pressurizing unit 38, so that
the surface 12a of the wafer 12 can be abraded without pressing the
abrasive face 52 by the pressing member 36.
Third Embodiment
[0119] In the first and the second embodiments, the inner enclosing
member 33 is separable from a base section 32, which includes the
upper section 30b and the outer enclosing member 30a, of the outer
head 30. In the third embodiment, the inner enclosing member 33 is
integrated with the base section 32 of the outer head 30.
[0120] In the case of integrating the inner enclosing member 33
with the base section 32 of the outer head 30, if air paths for
supplying the compressed air to the first and the second chambers
25 and 35 are separately formed, complex air-tight structures in
the first and the second chambers 25 and 35 are not required. The
structures can be simplified. In the case of employing the
pressurizing unit 28 of the first embodiment, an air path from the
pressurizing unit 28 is branched, and the branched paths are
respectively connected to the air path 27a and the inlet 39a. In
the case of employing the first and the second pressurizing units
38 and 39 of the second embodiment, the first pressurizing unit 38
is connected to the air path 27a and the second pressurizing unit
38 is connected to the inlet 39a.
[0121] In the third embodiment too, the force for pressing the
wafer 12 and the force for pressing the pressing member 36 onto the
abrasive face 52 can be respectively controlled by adjusting the
pressure in the first and the second chambers 25 and 35. Further,
the rotational speed of the wafer 12 and the pressing member 36 can
be respectively controlled by the inner and the outer head driving
units 44 and 54 (see FIG. 5). Therefore, the effects of the first
and the second embodiments can be gained by the abrasive machine of
the third embodiment.
[0122] In the above described embodiments, the wafer 12 is adhered,
on the holding face 22a of the holding plate 22, by water, but the
present invention is not limited to the embodiments.
[0123] For example, the wafer 12 may be sucked and held on the
holding face 22a of the holding plate 22. In this case, a vacuum
unit is communicated to the holding face 22a of the holding plate
22 so as to draw the wafer 12 by air suction.
[0124] The wafer 12 may be securely adhered on the holding face 22
by an adhesive.
[0125] The male tapered section 70 and the female tapered section
72 of the conventional abrasive machine (see FIG. 9) may be
employed in the present invention. By fitting the male tapered
section 70 in the female tapered section 72, the holding plate 22
can be precisely positioned, so that the wafer 12 can be positioned
or adhered at a correct position. Therefore, abrading accuracy and
abrading efficiency can be improved as well as the machine shown in
FIG. 9.
[0126] In the above described embodiments, the wafer 12, which has
been held by the holding plate 22, is pressed onto the abrasive
face 52 by air pressure. For example, liquid pressure, e.g., water
pressure, oil pressure, may be employed instead of the air
pressure.
[0127] In the above described embodiments, the surface 12a of the
silicon wafer 12 is abraded or polished as the work piece. Surfaces
of other wafer-shaped work pieces, e.g., glass plates, crystal
plates, can be abraded or polished properly.
[0128] The invention may be embodied in other specific forms
without departing from the spirit or essential characteristics
thereof. The present embodiments are therefore to be considered in
all respects as illustrative and not restrictive, the scope of the
invention being indicated by the appended claims rather than by the
foregoing description and all changes which come within the meaning
and range of equivalency of the claims are therefore intended to be
embraced therein.
* * * * *