U.S. patent application number 09/975528 was filed with the patent office on 2003-04-17 for system and method for non-contact wear measurement of dicing saw blades.
Invention is credited to Manor, Ran.
Application Number | 20030073382 09/975528 |
Document ID | / |
Family ID | 25523126 |
Filed Date | 2003-04-17 |
United States Patent
Application |
20030073382 |
Kind Code |
A1 |
Manor, Ran |
April 17, 2003 |
System and method for non-contact wear measurement of dicing saw
blades
Abstract
A method and apparatus for monitoring wear of a dicing saw
blade. The apparatus has a light source to emit light onto an end
surface of the saw blade; a sensor for receiving a reflection of a
portion of the light from the end surface of the saw blade; and a
processor coupled to the sensor for determining wear of the saw
blade based on an output from the sensor. The apparatus may also
display the wear rate of the saw blade, the present diameter of the
saw blade, and/or an estimated time for replacement of the saw
blade. The method comprises emitting light onto a cutting edge of
the saw blade; receiving a reflection of at least a portion of the
light from the edge of the saw blade; and determining wear of the
saw blade based on the reflected light.
Inventors: |
Manor, Ran; (Haifa,
IL) |
Correspondence
Address: |
RATNERPRESTIA
P O BOX 980
VALLEY FORGE
PA
19482-0980
US
|
Family ID: |
25523126 |
Appl. No.: |
09/975528 |
Filed: |
October 11, 2001 |
Current U.S.
Class: |
451/6 ; 451/41;
451/8 |
Current CPC
Class: |
B23Q 17/24 20130101;
B28D 5/022 20130101; B28D 5/0058 20130101; B23Q 17/09 20130101;
B23D 59/001 20130101 |
Class at
Publication: |
451/6 ; 451/8;
451/41 |
International
Class: |
B24B 049/00; B24B
051/00; B24B 001/00 |
Claims
What is claimed:
1. A device for monitoring wear of dicing saw blade, the device
comprising: a light source to emit light onto an end surface of the
saw blade; a sensor for receiving a reflection of a portion of the
light from the end surface of the saw blade; and a processor
coupled to the sensor for determining wear of the saw blade based
on an output from the sensor.
2. The device according to claim 1, wherein the sensor determines a
distance to the edge of the saw blade based on triangulation.
3. The device according to claim 1, further comprising first
focusing means for focusing the reflected light onto the plurality
of sensors.
4. The device according to claim 1, wherein the sensor is a
plurality of sensors.
5. The device according to claim 4, wherein each of the plurality
of sensors determines a respective distance to the edge of the saw
blade based on triangulation.
6. The device according to claim 4, further comprising a respective
plurality of first focusing means for focusing the reflected light
onto the plurality of sensors.
7. The device according to claim 1, wherein the monitoring device
is mounted on a cooling block of the saw blade.
8. The device according to claim 1, wherein the light impacts the
end of the saw blade substantially orthogonal to an axis of the saw
blade.
9. The device according to claim 1, wherein the light impacts the
surface of the saw blade substantially normal to a cutting edge of
the saw blade.
10. The device according to claim 1, wherein the sensor is a
position sensitive detector.
11. The device according to claim 1, wherein the sensor is a CCD
detector.
12. The device according to claim 1, wherein the sensor produces an
output based on a position of the reflected light on a surface of
the sensor.
13. The device according to claim 1, wherein the emitter is a laser
diode.
14. The device according to claim 1, wherein the emitter provides a
light output having a wavelength of between about 600 to 800
nm.
15. The device according to claim 1, wherein the processor
determines blade wear based on a measured distance between the
light source and a cutting edge of the saw blade.
16. The device according to claim 15, wherein the processor stores
successive wear data from the saw blade in a database.
17. The device according to claim 1, wherein the processor provides
a warning output based on a predicted wear of the saw blade, the
predicted wear determined from the successive wear data.
18. The device according to claim 1, wherein the predicted wear of
the blade is based on a comparison of the successive wear
information stored in the database.
19. The device according to claim 1, further comprising a monitor
for displaying at least one of i) a wear rate of the saw blade, and
ii) an estimated time for replacement of the saw blade.
20. The device according to claim 1, wherein saw blade wear is
determined in real time.
21. A method for monitoring wear of a dicing saw blade, the method
comprising the steps of: emitting light onto an cutting edge of the
saw blade; receiving a reflection of a portion of the light from
the edge of the saw blade; and determining wear of the saw blade
based on the reflected light.
22. The method according to claim 21, further comprising the step
of displaying at least one of i) a wear rate of the saw blade, and
ii) an estimated time for replacement of the saw blade.
23. A method for monitoring wear of a dicing saw blade, the method
comprising the steps of: emitting light onto a cutting edge of the
saw blade; receiving a reflection of a portion of the light from
the edge of the saw blade; triangulating a distance to the saw
blade base on the reflected light and determining wear of the saw
blade based on the triangulated distance.
24. A device for monitoring wear of dicing saw blade, the device
comprising: means to emit light onto a surface of the saw blade;
receiving means for receiving a reflection of a portion of the
light from the surface of the saw blade; and processing means
coupled to the receiving means for determining wear of the saw
blade based on an output from the receiving means.
25. The device according to claim 24, further comprising: display
means for displaying at least one of at least one of i) a wear rate
of the saw blade, ii) a diameter of the saw blade, and ii) an
estimated time for replacement of the saw blade.
26. The device according to claim 25, further comprising memory
means for storing the information displayed by the display
means.
27. The device according to claim 25, further comprising means for
predicting wear of the saw blade.
28. A device for use with a dicing saw to monitor wear of a dicing
saw blade, the device comprising: a light source to emit light onto
the saw blade; and a sensor for receiving at least a portion of the
light from the light source via the saw blade, the received portion
of the light based on a wear of the saw blade, wherein the device
is mounted on a cooling block of the dicing saw.
Description
FIELD OF THE INVENTION
[0001] This invention relates generally to the dicing of
semiconductor wafers, substrates and hard materials. More
specifically, the present invention relates to a system and method
to monitor and measure the wear of dicing saw blades used to dice
hard material substrates.
BACKGROUND OF THE INVENTION
[0002] Die separation, or dicing, by sawing is the process of
cutting a substrate into its individual circuit die with a rotating
circular abrasive saw blade. This process has proven to be the most
efficient and economical method in use today. It provides
versatility in selection of depth and width (kerf) of cut, as well
as selection of surface finish, and can be used to saw either
partially or completely through a wafer or substrate.
[0003] FIG. 1 is an isometric view of a semiconductor wafer 100
during the fabrication of semiconductor devices. A conventional
semiconductor wafer 100 may have a plurality of chips, or dies,
100a, 100b, . . . formed on its top surface. In order to separate
the chips 100a, 100b, . . . from one another and the wafer 100, a
series of orthogonal lines or "streets" 102, 104 are cut into the
wafer 100. This process is also known as dicing the wafer.
[0004] Dicing saw blades are made in the form of an annular disc
that is either clamped between the flanges of a hub or built on a
hub that accurately positions the thin flexible saw blade. The
blade is rotated by an integrated spindle-motor to cut into the
workpiece.
[0005] Wafer dicing technology has progressed rapidly, and dicing
is now a mandatory procedure in most front-end semiconductor
packaging operations. It is used extensively for separation of die
on silicon integrated circuit wafers.
[0006] Increasing use of microelectronic technology in microwave
and hybrid circuits, memories, computers, defense and medical
electronics has created an array of new and difficult problems for
the industry. More expensive and exotic materials, such as
sapphire, garnet, alumina, ceramic, glass, quartz, ferrite,
piezo-electric materials (PZT), alumina (Al.sub.2O.sub.3) and other
hard, brittle substrates, are being used mainly due to the
exploding markets in optical communication components and
telecommunications. In addition to these relatively new markets,
the traditional markets for hard materials, such as, sensors,
automotive components, ceramic ball grid array (CGBA), capacitors,
and PZT based surface acoustic wave filters and ultrasound
transducers are all exhibiting high growth rates in recent
years.
[0007] Dicing hard materials is a challenge for the dicing
industry. In order to maintain high dicing quality, namely, low top
and backside chipping, along with reasonable throughput, the use or
resinoid blades is desirable. A resinoid blade has a soft resin
based matrix acting as a binder of the diamond particles which, in
turn, perform the abrasive dicing process.
[0008] Relative to nickel binder type blades, predominately used in
the dicing process of integrated circuits, resinoid blades have a
blade wear rate that is larger than that of nickel binder type
blades by at least an order of magnitude. Although blade wear is
application dependent, an example may be useful to illustrate this
point. For a resinoid blade used in dicing a glass type substrate,
the blade wear is about five micron/meter of dicing length. By
contrast, for a nickel binder type blade, used in dicing silicon IC
wafers the blade wear is about 0.1 micron (or less) per meter of
dicing length.
[0009] Conventional methods of monitoring dicing saw blade wear are
time consuming As such, where high blade wear exists processing
throughput is significantly reduced. In one such conventional
contact method, a blade wear station, based on measuring the height
of the blade, is incorporated in the dicing area of the machine. To
accomplish this method 1) the height station and the blade tip are
brought on top of each other (height station below saw blade tip)
through motion in the X-Y plane; 2) the blade is gradually lowered
along the z-axis into the height station; 3) the blade tip is
brought into contact with the height station sensor to determine
the amount of wear of the blade; and 4) the height station and
blade are separated from one another and dicing continues. This
method is illustrated in U.S. Pat. No. 5,718,615 to Boucher et
al.
[0010] In another conventional non-contact method, Step 3) above is
modified such that the side of the blade interrupts the path of a
light source projected between two prisms to determine the height
of the blade and thereby the position of the end of the blade. This
method is illustrated in U.S. Pat. Nos. 5,353,551 and 5,433,649 to
Nishida.
[0011] The prior art is deficient, however, in that the
conventional methods are time consuming since the blade and height
monitoring station must be moved in X, Y and Z directions relative
to one another to begin the height measuring process and then
separated from one another after the blade wear is determined. It
is estimated that this process lasts a minimum of 15 seconds,
thereby significantly impacting device throughput, particularly in
applications where large blade wear is present.
[0012] There is a need to monitor blade wear during wafer or
substrate dicing for optimizing the dicing process and maintaining
a high cut quality so as not to damage the substrate, often
containing electronic chips or optoelectronic devices valued in the
many thousands of dollars. There is also a need to perform fast
monitoring so as to reduce cost of ownership.
SUMMARY OF THE INVENTION
[0013] In view of the shortcomings of the prior art, it is an
object of the present invention to help optimize the monitoring of
dicing saw blade wear.
[0014] The present invention is a device for monitoring dicing saw
blade wear. The device has a light source to emit light onto an end
surface of the saw blade; a sensor for receiving a reflection of a
portion of the light from the end surface of the saw blade; and a
processor coupled to the sensor for determining wear of the saw
blade based on an output from the sensor.
[0015] According to another aspect of the invention, the sensor is
a plurality of sensors.
[0016] According to a further aspect of the invention, the
monitoring device is mounted on a cooling block of the saw
blade.
[0017] According to still another aspect of the invention, a
position sensitive detector is used to sense the wear of the saw
blade.
[0018] According to yet another aspect of the present invention,
predicted wear of the blade is determined and communicated to the
operator and/or control center.
[0019] According to a further aspect of the invention, the wear
rate of the saw blade and/or an estimated time for replacement of
the saw blade may be communicated to the operator or control
center.
[0020] These and other aspects of the invention are set forth below
with reference to the drawings and the description of exemplary
embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The invention is best understood from the following detailed
description when read in connection with the accompanying drawing.
It is emphasized that, according to common practice, the various
features of the drawing are not to scale. On the contrary, the
dimensions of the various features are arbitrarily expanded or
reduced for clarity. Included in the drawing are the following
Figures:
[0022] FIG. 1 is an isometric view of a semiconductor wafer used to
form semiconductor devices;
[0023] FIG. 2 is a perspective view of an exemplary embodiment of
the present invention;
[0024] FIG. 3A is a diagram showing the blade wear monitoring
principle according to a first exemplary embodiment of FIG. 2;
[0025] FIG. 3B is a diagram showing the blade wear monitoring
principle according to a second exemplary embodiment of FIG. 2;
[0026] FIG. 4 is a flow chart illustrating a method for monitoring
saw blade wear according to an exemplary embodiment of the present
invention;
[0027] FIG. 5 is a diagram illustrating the details relating to
determining saw blade wear according to an exemplary embodiment of
the present invention; and
[0028] FIG. 6 is block diagram of a system according to an
exemplary embodiment of the present invention.
DETAILED DESCRIPTION
[0029] Referring to FIG. 2, an exemplary embodiment of the present
invention is shown. In FIG. 2, a portion of a dicing machine is
shown in which saw blade 220 is used to cut a workpiece (not shown
in this figure). Adjacent saw blade 220 is blade housing 210 which
also functions as a cooling block. Mounted above cooling block 210
is wear measuring device 200. As shown in FIG. 2, wear measuring
device 200 is fixedly disposed above saw blade 220. In the
exemplary embodiment, it is not necessary for blade 220 and wear
measuring device 200 to be moved relative to one another in order
to determine the wear of saw blade 200. As such, the time required
to perform this important step during the dicing process is
significantly reduced over that of the prior art, thereby
increasing process throughput.
[0030] FIG. 3A illustrates the details of the blade wear monitoring
system according to a first exemplary embodiment of the present
invention. In FIG. 3A, light source 300 emits light 301 passing
through optical elements 302 as focused light spot 303 onto an end
surface 222 (blade tip) of saw blade 220. In the embodiment, light
source 300, such as a diode laser, emits light in either the red
and near infrared region of the spectrum, such as between 600 and
800 nm, and preferably about 780 nm. The invention is not so
limited in that the wavelength of light may be selected based on
the type of sensors used.
[0031] As shown in FIG. 3A, detector 308 receives, at some angle,
through optic elements 306, reflections 304 of a portion of light
301 from end surface 222 of the saw blade 220. In a preferred
embodiment, the angle at which light is received by detector 308 is
about 43 degrees. The light spot focused on detector 308 is an
image of the light spot 303 projected from the light source 300
onto blade tip 222. A certain amount of light 310 will be scattered
from blade tip 222 and not received by sensor 308. In one
embodiment of the present invention, wear measuring device 200, is
a laser distance sensor Model LDS manufactured by Laser
Measurements International Delta, British Columbia, Canada, whereas
sensor 308 is a position sensitive detector (PSD). In other
embodiment, detector 308 may be a CCD device.
[0032] Since a change in the distance of the measured object from
light source 300 is reflected through a change of the image spot
position at the detector surface, the output electrical signal of
sensor 308 is therefore correlated to the position of the object
that the detected light was reflected from. In this case, the
position of end surface 222 of saw blade 220 from light source 300.
This measurement method is known as triangulation.
[0033] FIG. 3B illustrates the details of a second exemplary
embodiment of the present invention. In this embodiment, a
plurality of sensors 308, 309 receive, through optic elements 306,
307, reflections 304, 305, respectively, of a portion of light 301
from end surface 222 of the saw blade 220. The use of multiple
sensors will increase the accuracy of the system over the single
sensor system described above, nevertheless the triangulation
method described above is used in both embodiments. A certain
amount of light 310 will be scattered from end surface 310 and not
received by sensors 308, 309. As in the first embodiment, sensors
308, 309 are either position sensitive detectors (PSD) or CCD
devices. The electrical signal output by sensors 308, 309 are
correlated to the position of the object that the detected light
was reflected from. In this case, the position of blade tip 222 of
saw blade 220 relative to the light source 300.
[0034] In the exemplary embodiments the output voltage of sensors
308, 309 is linearly related to the distance from the light source
300 to end surface 222 of blade 220. To translate the change in
voltage output by sensors 308, 309 to a corresponding distance
variation, a calibration factor is applied. This calibration factor
is based on the specific design of the sensor and is thus supplied
by the manufacturer of the sensor. In the exemplary embodiment,
using a laser twin sensor such as a Model LTS 15/3 manufactured by
Laser Measurements International of Delta, British Columbia,
Canada, the calibration factor is 5 mV per 1 micron.
[0035] In the exemplary embodiment of FIG. 3B, it is contemplated
that the measurement range 312 of wear measuring device 200 is
about 2.9 microns. As shown in FIGS. 3A and 3B, wear measuring
device 200 is disposed above saw blade 220 such that the stand-off
distance 316 between wear measuring device 200 and saw 220 is about
15 mm. As a result, offset distance 314 is about 13.7 mm based on
Eq. 1:
OD=SO-MR/2 Eq. 1
[0036] where,
[0037] OD=offset distance 314;
[0038] SO=standoff distance 316;
[0039] MR=measurement range 312.
[0040] These ranges may vary, however, based on the specifications
of the sensor model.
[0041] A processor 604 (shown in FIG. 6) is coupled to each of
sensors 308, 309 for determining wear of saw blade 220 based on the
correlated output from sensors 308, 309.
[0042] The response of the PSD/CCD device enables monitoring of the
blade wear relative to an initial blade position. This is
illustrated in FIG. 5, in which light ray 303 from light source 300
is directed on the end of saw blade 220. As shown in FIG. 5, which
illustrates a single sensor system for simplicity, initially, when
saw blade 220 is new for example, light 303 is reflected from edge
502 of saw blade 220 as reflected light 506 to position 508 on
sensor 308. Sensor 308, in response to receiving these reflected
light beams, produces an output signal based upon the position of
the reflected light beam on the surface of sensor 308. In the case
of a new blade this value may be stored in a memory, for example,
in order to have a baseline for comparison.
[0043] Subsequently, after dicing portion of the workpiece, saw
blade 220 is once again measured to determine blade wear. In this
case, assuming that saw blade 220 has become worn, edge 504
represents the end of the saw blade. As a result, light 303 is
reflected as reflected rays 510, and received by sensor 308 at
position 512. Once again, sensor 308 outputs a signal indicative of
the position of the reflected light beam upon sensor 308. This
output signal is compared with the initial signal (representing a
new blade) to determine blade wear.
[0044] Of course, in the event the blade exposure has not reached a
minimum value, dicing operations may continue. If, on the other
hand, the blade exposure meets or exceeds the minimum blade
exposure requirements, the operator may be alerted to replace the
blade with a new one, or to replace a flange with a smaller outer
diameter in order to prevent damage to further processed
substrates.
[0045] FIG. 6 is a block diagram of an exemplary processing system
according to the present invention. In FIG. 6, sensors 308, 309 are
coupled to converter 604 to convert the analog outputs 600, 602 of
sensors 308, 309, respectively, into digital signals. These digital
signals are in turn input into processor 606 for processing. Of
course, in the event that sensors provide a digital output signal,
converter 604 may be eliminated. Processor 606 determines in real
time the blade wear based on the information received from sensors
308, 309 and the initial values stored in memory 608. Memory 608
may be any convention memory storage device or medium. It is also
contemplated that the operator may enter the initial values into
the system though conventional input devices such as a keyboard,
mouse, network connection, or wireless means.
[0046] Referring again to FIG. 6, processor 606 may also be coupled
to a display device 610 to display the results of the calculation,
such as the present wear of the saw blade and wear rate, and
provide guidance to the operator if the saw blade needs
replacement. It is also contemplated that the processor may
determine potential saw blade failure or life expectancy, based on
historic information maintained in memory 608 when compared to
measurement data for the saw blade. Likewise, this life expectancy
may be displayed on display 610 and periodically updated by
processor 606. Moreover, in terms of process control, a drastic
change in saw blade wear indicates process failure, for example
blade breakage.
[0047] FIG. 4 is a flow chart illustrating the method of monitoring
saw blade wear according to an exemplary embodiment of the present
invention. At Step 400, light is emitted onto the cutting edge of
the saw blade. At Step 405, sensors receive a reflection of a
portion of the light from the edge of the saw blade. At Step 410,
the distance between the sensor and the saw blade is measured based
on the position of the reflected light on the sensor surface. At
Step 415, the wear of the saw blade is determined based on a
comparison of the current and the previously measured distances
between the saw blade tip and the light source.
[0048] Although the invention has been described with reference to
exemplary embodiments, it is not limited thereto. Rather, the
appended claims should be construed to include other variants and
embodiments of the invention which may be made by those skilled in
the art without departing from the true spirit and scope of the
present invention.
* * * * *