BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION:
[0001] This invention relates to an apparatus for chamfering a semiconductor wafer and more
particularly to an apparatus for chamfering a notch of the wafer by the use of an
elastic grindstone.
DESCRIPTION OF THE PRIOR ART:
[0002] On account of effective application of photolithography, it has been customary for
wafers such as semiconductor wafers to have an orientation flat (hereinafter referred
to as "OF") formed thereon by grinding off to leave a short linear cut in part of
the periphery of a wafer thereby facilitating correct positioning of the wafer on
an exposure device.
[0003] The formation of the OF, however, inevitably results in removal of a large portion
of the wafer. Particularly in the production of wafers of a large diameter, the cumulative
amount of portions wasted by this removal is so large as to impair the yield of products
conspicuously. The fact that this impaired yield prevents expensive semiconductor
wafers from being efficiently utilized has posed a problem.
[0004] In the circumstances, the practice of forming a notch substantially in the shape
of the letter V or substantially in the shape of an arc to the periphery of a given
wafer has come to prevail for the purpose of efficiently utilizing produced wafers.
Particularly the V-shaped notches have been finding extensive utility by reason of
their outstanding accuracy of positioning.
[0005] Since the wafers are destined to be conveyed a number of times on production lines
as in the process for manufacture of devices, their peripheries are possibly subject
to chippings on colliding with parts of devices used in the manufacturing process
and the produced devices consequently suffer from degradation of characteristic properties.
It has been customary, therefore, for the wafers to have their peripheral parts chamfered.
SUMMARY OF THE INVENTION
[0006] The wafers furnished with a notch as described above, however, have come to entail
the drawback that the notch thereof is subject to chippings when the wafers are positioned
in the process of device production by aligning the notch to a pin of rigid material.
Since sharp edges of the wafers are not easily removed by machining, the sharp edges
conspicuously increase occurrence of dust and the effort to preclude infliction of
chippings fails. This fact has posed a problem too serious to be ignored. One solution
using an abrasive wheel having an edge which is shaped like a notch is described in
EP-A- 0 360 939.
[0007] This invention, initiated in the light of this problem, has as an object the provision
of an apparatus for chamfering a notch of a wafer, which apparatus is capable of easily
and accurately chamfering even edges such as of the notch and enabling the work of
chamfering the notch to be carried out in high efficiency. Moreover, this apparatus
enjoys simplicity of construction.
[0008] To accomplish the object described above, this invention contemplates an apparatus
which is provided with a rotary disklike grindstone, a wafer retaining mechanism for
retaining a wafer, and a drive mechanism for relatively moving the grindstone and
wafer, and characterized by the fact that the grindstone comprises an elastic matrix
material and a particulate abrasive buried or dispersed fast in the matrix material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Fig. 1 is a perspective explanatory diagram of an apparatus for chamfering a notch
of a wafer as an embodiment of this invention.
[0010] Fig. 2 is an explanatory diagram of the work of chamfering performed on the notch
in the direction of thickness of the wafer.
[0011] Fig. 3 is an explanatory diagram illustrating the elastic matrix part of a grindstone
in a state deformed under the pressure of the wafer.
[0012] Fig. 4 is an explanatory diagram of a wafer which has undergone the work of chamfering.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0013] In the apparatus of this invention for chamfering the notch of a wafer, the work
of chamfering the notch of the wafer is accomplished by relatively moving the grindstone
and wafer by dint of the operation of the drive mechanism. In this case, the grindstone
has the matrix thereof formed of an elastic material. Since the elasticity of the
matrix is utilized in causing the particulate abrasive to be pressed against the site
of chamfering, the survival of any sharpness on the chamfered part can be easily precluded.
[0014] Since the grindstone has the matrix thereof formed of an elastic material, the cross
section of the circumferential edge of the grindstone has a shape roughly resembling
the letter V having a radius in the bottom part thereof. When the angle formed between
the oblique lines of the letter V is slightly larger than the corresponding angle
of the plan figure of the notch and the radius at the leading terminal of the notch
in the direction of center of the wafer and the grindstone, during the grinding operation,
is kept applied to the notch subjected to the grinding with the center of rotation
of the grindstone set at a position higher than the position of the wafer surface,
the chamfering of the notch can be completed by simply moving the grindstone only
slightly in the vertical direction. By suitably adjusting the softness of the matrix
of the grindstone, the formation of a concave surface in the chamfered part due to
the contour of the grindstone is precluded and the chamfering of-the notch is ideally
effected to give rise to a smoothly curved rather outwardly protruding surface. In
this case, in the first, second, and third drive mechanism recited in claim 3, particularly
the first and second drive mechanism are used for accurately controlling and adjusting
the position of the grindstone prior to the chamfering work.
[0015] The apparatus for chamfering the notch of a wafer according to this invention will
be described below with reference to the accompanying drawings which illustrate one
embodiment of this invention.
[0016] In Fig. 1, the reference numeral 10 stands for an apparatus for chamfering the notch
as one embodiment of this invention. This notch chamfering apparatus 10 comprises
a wafer retaining mechanism 14 capable of retaining a wafer 12 in a prescribed posture,
a first drive mechanism 15 capable of rotating the wafer 12 within a prescribed range
of angle around (in the direction of the arrow ϑ ) an axis perpendicular to the main
surface of the wafer 12, a rotary drive mechanism 18 capable of setting a disklike
grindstone 16 in such a manner that the surface of the grindstone 16 intersects (perpendicularly
in this embodiment) the surface of the wafer 12, a second drive mechanism 20 provided
in the wafer retaining mechanism 14 for producing a relative motion of the grindstone
16 and wafer 12 toward or away from each other in the direction of radius of the grindstone
16 (in the direction of arrow X), and a third drive mechanism 22 provided in the rotary
drive mechanism 18 for producing a relative motion of the grindstone 16 and wafer
12 toward or away from each other in the direction of wall thickness of the wafer
12 (in the direction of the arrow Z).
[0017] The wafer retaining mechanism 14 is provided with a base stand 28 and the base stand
28 is provided with a cylindrical part 30. A rotary stand 32 is disposed on the cylindrical
part 30. In the upper end surface of this rotary stand 32, a plurality of suction
holes 34 communicating with a vacuum pump not shown in the diagram and serving to
attract the wafer 12 by suction are formed. The first drive mechanism 15 is provided
with a pulse motor 36 which is a servomotor in type. A feed screw 38 is connected
to the pulse motor 36 and the feed screw 38 is coaxially interlocked with the rotary
stand 32.
[0018] The second drive mechanism 20 is provided with a pulse motor 40. A feed screw 42
which is connected to the rotary shaft of the pulse motor 40 is interlocked with the
wafer retaining mechanism 14. The rotary drive mechanism 18 is provided with an electric
motor 44 and the grindstone 16 is rotatably fixed to a rotary shaft 46 of the electric
motor 44. With this rotary drive mechanism 18 is interlocked a feed screw 50 which
is connected to a pulse motor 48 forming a component of the third drive mechanism
22.
[0019] The grindstone 16 comprises a matrix part 52 formed of an elastic material such as,
for example, a synthetic resin type material like urethane rubber and a particulate
abrasive 54 buried in a comparatively soft peripheral surface portion of the matrix
part 52 destined to serve as a grinding surface. The grindstone 16 may be otherwise
formed by dispersing the particulate abrasive in the synthetic resin material and
shaping the resultant dispersion and the peripheral part of this grindstone may be
used for the grinding aimed at by this invention.
[0020] Now, the operation of the notch chamfering apparatus 10 constructed as set forth
above will be described below.
[0021] First, the disklike wafer 12 is set in place on the rotary stand 32 which is one
of the components of the wafer retaining mechanism 14. By the action of the vacuum
pump not shown in the diagram, the wafer 12 is attracted through the suction holes
34 to the rotary stand 32 by suction. After a notch 24 of the wafer 12 and the grindstone
16 have been disposed at prescribed positions necessary for perpendicular intersection
of their respective surfaces, the first drive mechanism 15 to third drive mechanism
22 are selectively or synchronously driven and controlled. As a result, by the action
of the pulse motor 36 and through the medium of the feed screw 38, the rotary stand
32 is rotated at a prescribed speed in the direction of the arrow ϑ . At the same
time, the feed screw 42 is rotated by the pulse motor 40 to move the wafer retaining
mechanism 14 forward and backward in the direction of the arrow X. In the meanwhile,
the grindstone 16 is rotated through the medium of the rotary shaft 46 by the driving
action of the electric motor 44. Consequently, the wafer 12 is rotated in the direction
of the arrow ϑ and the chamfering work is performed within a relatively small width
on the notch 24 of the wafer 12 in the direction of circumference of the notch 24
to form the innermost of the angular part 24a while the wafer 12 and the grindstone
16 in rotation are moved toward or away from each other (Fig. 2).
[0022] While the chamfering work performed on the angular part 24a in the direction of circumference
of the notch 24 is continued, the grindstone 16 is moved along the angular part 24a
at a comparatively low speed in the direction of the arrow as illustrated in Fig.
2. To be specific, when a signal to drive is input into the pulse motor 48 which is
one of the components of the third drive mechanism 22, the feed screw 50 is rotated
through the medium of this pulse motor 48 in the given direction and the rotary drive
mechanism 18 interlocked with this feed drive 50 is slowly moved in the direction
of the arrow Z₁. Synchronously with this motion, the pulse motor 40 is set into motion
to move the grindstone 16 and the wafer 12 relatively in the direction of the arrow
X₁ and position the grindstone 16 relative to the angular part 24a. After the chamfering
work to be performed, within the first width as described above, in the direction
of circumference of the notch 24 has been completed, the chamfering work is repeated
on a neighboring width of the angular part 24a in the same direction as the first
try to cover the full thickness of the angular part 24a.
[0023] Then, a circumferential surface part 24b and an angular part 24c in reverse to the
angular part 24a of the wafer 12 are similarly subjected to a continuous shaping work
on a plurality of working rounds as spaced by predetermined widths of interval. Here,
the grindstone 16 is moved in the direction of the arrow Z₂ while the outer circumferential
surface part 24b perpendicular to the main surface of the wafer 12 is undergoing the
chamfering work, whereas the grindstone 16 and the wafer 12 are relatively moved respectively
in the direction of the arrows X₂ and Z₃ while the angular part 24c is undergoing
the chamfering work. This procedure brings about the effect of enabling the chamfering
work of the wafer 12 in the circumferential direction and in the direction of the
wafer thickness to be continuously and efficiently carried out.
[0024] In this case, since the grindstone 16 of this embodiment has the matrix part 52 thereof
formed of an elastic material, the chamfering work of the wafer 12 can be carried
out with this grindstone 16 kept pressed against the wafer 12 with predetermined pressure.
Specifically, when the grindstone 16 is pressed against the wafer 12 as illustrated
in Fig. 3, the comparatively soft circumferential surface part of the matrix part
52 which is one of the component of this grindstone 16 is deformed to be pressed against
the wafer 12. Consequently, the abrasive particles 54 buried in the circumferential
surface part come into generous contact with the wafer 12 and grind the wafer 12,
particularly the corner parts A to D of the surface of the wafer 12 subjected to grinding
(as indicated by a broken line in Fig. 4), and give rise to radiuses, one in each
of the corner parts A to D (as indicated by a solid line in Fig. 4). This fact gives
rise to the effect of obviating the necessity for complicate control and allowing
easy formation of radiuses with a simple construction without inducing infliction
of cracks and chippings on the corner parts A to D.
[0025] Particularly, the fact that the wafer 12 and the grindstone 16 are so disposed that
the respective surfaces thereof intersect perpendicularly gives birth to the advantage
of enabling the chamfering work of high accuracy to be performed, by dint of the grinding
surface of the grindstone 16, on the surface of the notch 24 which is appreciably
small as compared with the size of the wafer 12.
[0026] This embodiment has been described as representing a case in which the chamfering
work of the whole of the notch 24 is effected by moving the grindstone 16 in the direction
of thickness of the wafer 12 (in the direction of the arrow Z) while continuing the
chamfering work in the circumferential direction of the notch 24. Optionally, this
procedure may be reversed by moving the grindstone 16 and the wafer 12 in the circumferential
direction of the wafer 12 while continuing the chamfering work on the notch 24 in
the direction of thickness thereof.
[0027] To be specific, the chamfering work is performed on the notch 24 in part of the direction
of thickness by synchronously driving and controlling the second drive mechanism 20
and the third drive mechanism 22 thereby moving the wafer 12 in the direction of the
arrow X and moving the grindstone 16 in the direction of the arrow Z and, at the same
time, the wafer 12 is slowly rotated around the central axis thereof (in the direction
of the arrow ϑ ) by rotating the pulse motor 36 at a comparatively low speed. As a
result, the grindstone 16 is enabled to perform the chamfering work continuously on
the notch 24 in the circumferential direction while chamfering the notch 24 in the
direction of the wafer thickness.
[0028] The apparatus of this invention for chamfering the notch of the wafer produces the
following effects.
[0029] During the chamfering work performed on the notch of the wafer through relative motion
of the grindstone and wafer by the operation of the driving mechanisms, the survival
of any sharpness on the chamfered part is easily precluded because the matrix part
forming one component of the grindstone is formed of an elastic material and the particulate
abrasive is pressed against the site of chamfering by dint of the elasticity of this
elastic material. By the simple construction resorting to the use of this elastic
grindstone, the chamfering work of the notch of a small size in the circumferential
direction and/or in the direction of the wafer thickness can be carried out very accurately
and efficiently.
1. An apparatus (10) for chamfering a notch (24) of a wafer (12), provided with a rotary
disklike grindstone (16), a wafer retaining mechanism (14) for retaining the wafer
(12), and a drive mechanism (15, 20, 22) for relatively moving said grindstone (16)
and wafer (12), and characterized by the fact that said grindstone (16) comprises
an elastic matrix material (52) and a particulate abrasive (54) buried or dispersed
fast in said matrix material (52).
2. An apparatus according to claim 1, wherein said wafer retaining mechanism (14) is
capable of disposing said wafer (12) in such a manner that the surface of said wafer
(12) intersects the surface of said grindstone (16).
3. An apparatus according to claim 1, wherein said drive mechanism comprises a first
drive mechanism (15) capable of rotating said wafer (12) within a predetermined range
of angle (ϑ) around the central axis thereof thereby enabling the surface of the notch
(24) of said wafer (12) subjected to grinding to be continuously positioned relative
to the grinding surface of said grindstone (16), a second drive mechanism (20) capable
of relatively moving said grindstone (16) and wafer (12) toward or away from each
other, and a third drive mechanism (22) capable of relatively moving said grindstone
(16) and wafer (12) forward and backward in the direction of thickness of said wafer
(12).
4. An apparatus acccording to claim 1, wherein said matrix material (52) is a synthetic
resin type material.
1. Vorrichtung (10) zum Anschrägen einer Kerbe (24) eines Wafers (12), welche mit einem
drehenden scheibenähnlichen Schleifstein (16), einem Waferhaltemechanismus (14) zum
Halten des Wafers (12) und einem Antriebsmechanismus (15, 20, 22) für ein relatives
Bewegen des Schleifsteins (16) und des Wafers (12) versehen ist, dadurch gekennzeichnet,
daß der Schleifstein (16) ein elastisches Matrixmaterial (52) und ein aus Partikeln
bestehendes Schleifmaterial (54) aufweist, welches in dem Matrixmaterial (52) eingebettet
oder dispergiert ist.
2. Vorrichtung nach Anspruch 1, bei welcher der Waferhaltemechanismus (14) das Wafer
(12) in einer solchen Art und Weise anordnen kann, daß die Oberfläche des Wafers (12)
die Oberfläche des Schleifsteins (16) kreuzt.
3. Vorrichtung nach Anspruch 1, bei welcher der Antriebsmechanismus einen ersten Antriebsmechanismus
(15) aufweist, der das Wafer (12) innerhalb eines vorbestimmten Winkelbereichs (O)
um seine mittlere Achse drehen kann und dadurch ermöglicht, daß die dem Schleifen
zu unterwerfende Oberfläche der Kerbe (24) des Wafers (12) relativ zu der Schleiffläche
des Schleifsteins (16) kontinuierlich positioniert wird, einen zweiten Antriebsmechanismus
(20), welcher den Schleifstein (16) und das Wafer (12) aufeinander zu und weg voneinander
relativ bewegen kann, und einen dritten Antriebsmechanismus (22), welcher den Schleifstein
(16) und das Wafer (12) vorwärts und rückwärts in der Richtung der Dicke des Wafers
(12) relativ zueinander bewegen kann.
4. Vorrichtung nach Anspruch 1, bei welcher das Matrixmaterial (52) ein Kunstharzmaterial
ist.
1. Dispositif (10) pour chanfreiner une entaille (24) d'une plaquette (12), comprenant
une meule circulaire en forme de disque (16), un organe de maintien (14) de la plaquette
pour maintenir la plaquette (12), et un mécanisme d'actionnement (15, 20, 22) pour
faire se déplacer relativement l'une par rapport à l'autre ladite meule (16) et ladite
plaquette (12), caractérisé en ce que ladite meule (16) comprend un matrice en un
matériau élastique (52), et un abrasif particulier (54), enfoui ou dispersé fermement
dans ledit matériau de la matrice (52).
2. Dispositif selon la revendication 1, caractérisé en ce que ledit mécanisme de maintien
de la plaquette (14) est susceptible de disposer ladite plaquette (12) de telle manière
que la surface de ladite plaquette (12) intersecte la surface de ladite meule (16).
3. Dispositif selon la revendication 1, caractérisé en ce que ledit organe d'actionnement
comprend :
- un premier mécanisme d'actionnement (15), susceptible de faire tourner la plaquette
(12) selon un intervalle prédéterminé de l'angle (ϑ) par rapport à l'axe central de
telle sorte à permettre à la surface de l'encoche (24) de ladite plaquette (12) soumise
au meulage, d'être positionnée de manière continue relativement à la surface de meulage
de ladite meule (16) ;
- un second mécanisme d'actionnement (20) susceptible de déplacer relativement ladite
meule (16) et la plaquette (12) l'une vers l'autre ou l'une de l'autre ;
- et un troisième mécanisme (22), susceptible de déplacement relativement ladite meule
(16) et la plaquette (12) en avant ou en arrière dans la direction de l'épaisseur
de ladite plaquette (12).
4. Dispositif selon la revendication 1, caractérisé en ce que le matériau de la matrice
(52) est un matériau de type résine synthétique.