U.S. patent application number 12/299358 was filed with the patent office on 2009-12-03 for method and apparatus for chemical mechanical polishing of large size wafer with capability of polishing individual die.
Invention is credited to Craig Burkhart, Yuzhou Li, Qingjun Qin.
Application Number | 20090298388 12/299358 |
Document ID | / |
Family ID | 38668549 |
Filed Date | 2009-12-03 |
United States Patent
Application |
20090298388 |
Kind Code |
A1 |
Li; Yuzhou ; et al. |
December 3, 2009 |
METHOD AND APPARATUS FOR CHEMICAL MECHANICAL POLISHING OF LARGE
SIZE WAFER WITH CAPABILITY OF POLISHING INDIVIDUAL DIE
Abstract
A novel polisher for chemical mechanical planarization process
is described. The polisher design can have many variations. For
process development and consumable evaluation, the CMP process can
be performed on a single die or a section of the wafer. The size of
testing wafer can be as small as 2'' and as large as 18''.
Furthermore, several variations can characterize the slurry for
their static etch rate, dynamic etch rate, material removal rate,
and viscosity in a single experiment. For production level wafer
processing, Chemical Mechanical Polishing of all dies on the wafer
surface is achieved by using multi-armed polishing heads or a
single polishing head with small piece of a pad at the bottom of
the head. The within wafer uniformity can be easily controlled and
the equipment can be easily scaled up or down. This inventive
design may translate to significant cost reduction for wafer
processing at production level as well as evaluation of consumables
at research and development level.
Inventors: |
Li; Yuzhou; (Norwood,
NY) ; Qin; Qingjun; (Potsdam, NY) ; Burkhart;
Craig; (Potsdam, NY) |
Correspondence
Address: |
FROMMER LAWRENCE & HAUG
745 FIFTH AVENUE- 10TH FL.
NEW YORK
NY
10151
US
|
Family ID: |
38668549 |
Appl. No.: |
12/299358 |
Filed: |
May 3, 2007 |
PCT Filed: |
May 3, 2007 |
PCT NO: |
PCT/US07/68116 |
371 Date: |
August 3, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60746320 |
May 3, 2006 |
|
|
|
Current U.S.
Class: |
451/6 ; 451/159;
451/41; 451/8 |
Current CPC
Class: |
B24B 21/04 20130101;
B24B 37/105 20130101; B24B 37/04 20130101; B24B 49/10 20130101;
B24B 57/02 20130101; B24B 37/30 20130101 |
Class at
Publication: |
451/6 ; 451/41;
451/159; 451/8 |
International
Class: |
B24B 1/04 20060101
B24B001/04; B24B 7/22 20060101 B24B007/22; B24B 49/10 20060101
B24B049/10; B24B 49/12 20060101 B24B049/12 |
Claims
1. A method of chemical mechanical polishing of a surface of a
substrate to remove selected portions thereof comprising: (i)
maintaining at least a portion of the surface of the substrate in
sliding fractional contact with the polishing pad until the
selected portions of the surface of the substrate are removed; (ii)
polishing one area on a blanket/patterned wafer, containing one or
more dies, using a single polishing head with a small piece of
commercial CMP pad or a pad under evaluation; and (iii) polishing a
patterned wafer using multi-arm polishing head with each polishing
arm corresponding to a die on the patterned wafer wherein the
die(s) on the Patterned wafer desired to be polished is processed
and the remaining dies are protected by a cover or a mask.
2. (canceled)
3. The method of claim 1, wherein only a portion of the surface of
the substrate is polished by a single polish head or multi-arm
polish head with multiple pads while the rest area of the surface
of the substrate to be polished is protected.
4. An apparatus for chemical mechanical polishing of a surface of a
substrate to remove selected portions thereof comprising: (i) a
fixed platen to hold the wafer to be polished, the wafer holder is
changeable, and the size of the holder adjustable to fit different
size of the wafer; (ii) a cam with an offset with the motor axle to
make orbital motion of the polishing pad and achieves the same
relative velocity between each point on the pad and the area to be
polished; (iii) a device for providing an oscillatory motion on the
surface of a single die; (iv) a disk to hold the multi-arm polish
head system; (v) a slurry delivery system in which the slurry can
be supplied to each individual die on the patterned wafer
separately; (vi) a two-motor system, one motor rotates the disk
that holds the second motor and the second motor rotates the pad in
a same rotation speed and the same direction as that of the first
motor and thus the same relative velocity between each point on the
pad and the area to be polished is achieved; (vii) a two-lever
adjustment system to control the position of the polish head and
the wafer whereby all the dies on the patterned wafer can be
polished; (viii) adjustable legs for tilting the whole apparatus;
(ix) a slurry collection system to collect used slurry; and (x) a
replaceable pad conditioning disk.
5. The apparatus of claim 4, wherein the tubes of the slurry
delivery system are distributed in parallel.
6. A device for the evaluation of the performance and
characteristics of a slurry comprising of a slurry chamber, a
rotary wafer carrier that is vertically placed and fixed on lateral
movement, a rotary pad carrier that is movable along its lateral
axis, a sensor which measures the film thickness change in-situ,
and a sensor which measures the resistance exerted on to the rotary
movement of the pad carrier.
7. The device of claim 6, lateral and rotary movements for the pad
and wafer carriers are accomplished by DC motors.
8. The device of claim 6, lateral and rotary movements of the pad
carrier are accomplished by the use of a magnetic levitation
system.
9. The device of claim 6, the film thickness change is measured by
14-point probe or Eddy current system for metal films.
10. The device of claim 9, wherein the film is a dielectric film
and the measurement is made by an optical sensor.
11. The device of claim 10, wherein an acoustic sensor for
measuring the film thickness change for metal and non-metal is
simultaneously used.
12. A polisher that utilizes polishing tape for IC wafer processing
comprising of a slurry delivery system, a tape management system, a
guiding system for the tape, and optionally a system for tape
cleaning, conditioning, and re-use.
13. The polisher of claim 12, the tape can be made with natural,
process natural materials or synthetic materials.
14. The polisher of claim 12, wherein the tape management system is
selected from the group consisting of a controller of tape tension,
a controller of tape movement, a tape cleaner, a tape conditioner,
an embosser of patterns before the tape reaches the wafer, a
flipping mechanism that allows the use of either side of the tape
and combinations thereof.
15. The polisher of claim 12, wherein the tape guiding system may
include a solid roller or a block that controls the distance
between the tape and the wafer.
Description
INCORPORATION BY REFERENCE
[0001] Any foregoing applications and all documents cited therein
or during their prosecution ("application cited documents") and all
documents cited or referenced in the application cited documents,
and all documents cited or referenced herein ("herein cited
documents"), and all documents cited or referenced in herein cited
documents, together with any manufacturer's instructions,
descriptions, product specifications, and product sheets for any
products mentioned herein or in any document incorporated by
reference herein, are hereby incorporated herein by reference, and
may be employed in the practice of the invention.
FIELD OF THE INVENTION
[0002] This invention relates to a method of chemical mechanical
polishing (CMP) for microelectronics applications. Specifically,
the invention is directed to an apparatus of chemical mechanical
polishing used for large size patterned/blanket wafer polishing, a
process allowing polishing an individual die at a time, and a
method for chemical mechanical polishing slurry and process
evaluation.
BACKGROUND INFORMATION
[0003] Chemical mechanical polishing has become an essential
technology for fabrication of semiconductor devices and recording
head for hard disk drives. In a typical chemical mechanical
polishing (CMP) process, the wafer to be polished is held by a
rotating carrier or polishing head, the pad is mounted on a
rotating platen or table, and the slurry is delivered into the
space between the wafer and the pad. Generally, the wafer, blanket
or with patterns, has a thin film of metal, oxide, polysilicon, or
other materials. The polyurethane pad, with grooves and asperities
on the surface, brings slurry to be in contact with the wafer and
takes removed residues away from the polish zone. The slurry,
containing abrasives, oxidizer, complexing agent, inhibiting agent,
passivating agent, surfactant, and with an appropriate pH, provides
chemical reaction to soften the wafer surface and mechanical
removal to remove the reacted layer by abrasive particles.
Abrasive-free slurry is also known (U.S. Pat. Nos. 6,800,218 and
6,451,697), in which the abrasive particles and surfactant used to
stabilize the colloidal system are removed.
[0004] A CMP apparatus, or CMP polisher, is an equipment to realize
the CMP process. A typical CMP polisher mainly consists of three
parts: the carrier, the platen, and a slurry delivery system.
Besides holding the wafer, the carrier also provides the functions
of rotating the wafer and adjusting down force & back pressure.
The platen rotates the pad to polish the wafer, which, generally,
is located below the wafer to be polished. In an orbital CMP
polisher, the pad has an orbital motion and thus each point on the
pad describes a circle along an orbit. The relative motion between
the wafer and the pad is important for a uniform material removal
from every point on the wafer surface. Ideally, it is expected to
achieve the same or similar velocity for each point on the wafer
relative to the pad, which can be realized by maintaining the same
or similar rotation speed and the same rotation direction for both
the carrier and the platen in rotational polisher. Atypical
polisher is designed to polish the entire wafer.
[0005] It is commonly accepted that, in a production environment, a
uniform polishing of the entire wafer is a prerequisite to achieve
the desired global planarity. For a simple evaluation of CMP
process or consumables such as slurry, it is desirable to polish
only a small portion of the wafer in order to cut down the cost of
using up the entire wafer with single evaluation. This is often
accomplished by using a small bench top polisher and a small
patterned wafer (e.g. 2'' diameter) cut out from a larger wafer
(e.g. 8''). Due to the practical difficulty in producing a 2''
wafer with smooth edge, only 4 to 5 2'' wafers can be produced from
a single 8'' wafer. Furthermore, on the 2'' wafers produced by this
method only one die is usable. Another motivation for adapting this
approach is the ever increasing cost and complexity of a full wafer
or production polisher. Therefore, a polisher that is capable of
polishing a small portion of the wafer without cutting the wafer
down to small pieces is certainly a valuable tool for CMP process
and consumable evaluation. This invention addresses this issue with
an inventive polisher design.
[0006] When Chemical Mechanical Polishing was first adopted for
wafer processing by semiconductor industry, the wafer sizes were 2
to 6'' in diameter. The traditional silicon grinder/polisher design
was essentially adopted without much modification. As matter of
fact, the basic platform has practically unchanged for the past
twenty years since the adaptation of CMP into wafer processing such
as dielectric, metal, and copper planarization. It is widely
recognized that, with the ever increase in wafer size, a number of
scale up issues are becoming more and more apparent. Significant
effort has been spent and complicated schemes must be in place to
maintain the within-wafer-non-uniformity for wafers larger than 200
mm. Due slurry residence time increase, the temperature profile
underneath the wafer during the polishing is significantly
different from that for smaller wafers. It is increasingly
difficult to optimize planarity at global level without severe over
polishing at some local levels. Furthermore, a compromise of such
at lower level poses greater threat on defectivity at higher level.
This will only become even more severe for 450 mm wafers and
beyond. In other words, with the significant increase in wafer size
and challenges to maintain within wafer uniformity and defectivity,
the conventional design is no longer a best choice. This invention
addresses this issue with a set of new polisher design that can
meet the challenges for large wafer processing while maintaining
the control on local and global planarity.
SUMMARY OF THE INVENTION
[0007] Unlike the design in a conventional polisher, the new design
described in this invention places the focus on each individual
dies that need to be processed. In another word, at least with one
of the designs, there will be many small arms that will work
parallel on different dies individually. According to the present
invention, the forgoing and other aspects are achieved by but not
limited to a platen to hold the wafer, a multiple-arm system with
polish heads to hold the pad, a slurry delivery system, a pressure
control system, a separate pad conditioning disk, a part to collect
used slurry, and a system consisting of motor(s) to drive the
polish head and drainage for used slurry. As a variation of the
design described above, a small section of the wafer that contains
several dies can be polished together. When several such sections
are polished in concert, the entire wafer is processed at the same
time. As a further modification of the design described above, an
even larger portion of the wafer can be polished using a pad
similar to the wafer in size. Such a device contains the needed
sensors to report information such as slurry viscosity, static etch
rate, dynamic etch rate, polishing rate at low down force, and
friction between the pad and wafer upon initial contacts. The main
application of this device is to provide useful information on the
characteristics and performance of consumables such as slurry and
pad.
[0008] Another aspect of the present invention is a method of
manufacturing a semiconductor device. The method is achieved by
using the present invention and a slurry to planarize a thin film
on the wafer, such as Cu or Cu alloy film on a dielectric layer,
oxide, barrier layer, or low material on wafer surface by CMP.
[0009] The third aspect of the present invention is an effective
and efficient method to achieve planarization on the selected area
on the wafer surface or the entire wafer.
[0010] In an embodiment of the present invention as shown in FIG.
1, the wafer is hold on the platen, which is fixed and located
below the multiple arms with polish heads, whereas the pads are
attached to these polishing heads. The pad selection is mainly
based on the film to be polished (copper, dielectric, barrier,
metal, etc). There will be multiple sets of these polishing heads.
Therefore, while one set is in operation of polishing, the other
sets can be either conditioned or exchanged. This should eliminate
or significantly reduce the tool down time. Whenever it is desired,
the wafer can be covered by a specifically designed mask (FIG. 2)
with the same number of windows as that of the dies on the wafer.
These windows can be open, if the die located at the window will be
polished; or closed so that the thin film is protected by the
cover.
[0011] It is noted that in this disclosure and particularly in the
claims and/or paragraphs, terms such as "comprises", "comprised",
"comprising" and the like can have the meaning attributed to it in
U.S. Patent law; e.g., they can mean "includes", "included",
"including", and the like; and that terms such as "consisting
essentially of" and "consists essentially of" have the meaning
ascribed to them in U.S. Patent law, e.g., they allow for elements
not explicitly recited, but exclude elements that are found in the
prior art or that affect a basic or novel characteristic of the
invention.
[0012] Additional aspects of the present invention are apparent to
those skilled in this technology from the following detailed
description, wherein embodiments of the present invention are
described, simply by way of illustration of the best mode
contemplated for carrying out the present invention. As will be
realized, the present invention is capable of other and different
embodiments, and its several details are capable of modifications
in various obvious respects, all without departing from the present
invention. Accordingly, the drawings and description are to be
regarded as illustrative in nature, and not as restrictive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 depicts the overall design of a polisher with
multiple polishing heads.
[0014] FIG. 2 depicts a schematic of a polishing head.
[0015] FIG. 3 depicts a schematic of a wafer holder and mask for
patterned wafer.
[0016] FIG. 4 depicts a schematic of a single armed pad on a
typical die.
[0017] FIG. 5 depicts a schematic of a slurry delivery system.
[0018] FIG. 6 depicts the overall design of a polisher with a
single polishing head (top view).
[0019] FIG. 7 depicts the overall design of a polisher with a
single polishing head (side view).
[0020] FIG. 8 depicts a schematic of a single polishing head.
[0021] FIG. 9 depicts a schematic of a disk that holds the
polishing pad.
[0022] FIG. 10 depicts a schematic of a cam that drives the pad
holder.
[0023] FIG. 11 depicts a schematic of an 8'' wafer holder.
[0024] FIG. 12 depicts a schematic of a slurry evaluator.
[0025] FIG. 13. shows the capability of six axis magnetic
levitation stage designed for photolithographic application.
[0026] FIG. 14 shows the basic principle of using levitation
technique to measure viscosity of a fluid.
[0027] FIG. 15 shows the simulation of material removal rate vs.
inter plate distance between the pad and wafer.
[0028] FIG. 16 depicts the schematic of a polisher uses polishing
tape.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] The present invention enables effective and efficient
planarization of large wafer (12'', 18'',and beyond) with the
capability of polishing individual die that need to be processed
and easy control of within wafer uniformity, providing advantages
over conventional CMP polisher. The present inventive design
departs significantly from the traditional polisher design by
focusing on each individual dies that need to be processed.
[0030] Aspects of the present invention are implemented by
employing single polishing head with pad or multi-arms with
polishing head to process one die or multiple dies on the wafer
surface. In addition, the wafer is stationary. Conventional CMP
polisher employs a large single pad, but only a portion of the pad
is used as polish area. With this platform, it is difficult to
process lager and lager wafers without the increase of pad size and
the footprint of a polisher. The present invention overcomes this
difficulty by switching the relative positions of the wafer and the
pad and employing a set of polishing head each equipped with a
small pad. Therefore, the footprint of a polisher according to
present invention is only approximately 1/20 of the size of a
conventional polisher. Furthermore, the wafer holder can be easily
upgraded to accommodate larger wafers. More specifically, the new
polisher can scale down to polish 2'' wafers and up to handle 18''
without any further capital investment. As a result of such
extendibility, the cost of ownership of such a polisher will be
significantly lower than that of a conventional polisher. Without
having to provide movement of large platen and heavy wafer carrier,
the energy consumption by the new polisher will be significantly
lower that its counterpart with a conventional design.
[0031] One of the embodiments of the present invention is achieved
by many small arms with small pieces of pad at the bottom that work
parallel on dies individually, as shown in FIG. 1. These arms are
fixed to a disk that has the same number of holes as that of the
dies on the wafer, as shown in FIG. 2. Each arm corresponds to a
hole where the arm can be fixed or removed according to the
processing requirement of the die corresponding to the hole. The
disk is driven by a motor with a mechanic rod to do an oscillatory
movement. Therefore, each pad will also move in the same manner on
the corresponding die surface, as shown in FIGS. 3 and 4. FIG. 4
also shows that movement of a single pad on a typical die, the
relative velocity and central location between the pad and wafer
are mechanically controlled and computer programmed to vary during
the polishing. The net averaging effect of these variations is to
allow each location on the wafer to experience the polishing tape
from all directions.
[0032] The slurry is supplied to each die on the patterned wafer
individually and the slurry delivery can be turned off if
necessary, as shown in FIG. 5. A slurry collection system is
designed around the wafer holder to collect the used slurry in the
case that the used slurry is needed to be collected for further
analysis. The operation of the polishing process on the present
invention is, but not limited to, performed on a tilted new
polisher in order to provide a better slurry fluid mechanics on the
wafer surface. The tilting of the present invention can be
obtained, but not limited, by adjustable legs whose heights can be
adjusted to a required level. The angle of the tilted wafer surface
can be 10 to 45 degrees. The pressure control is realized by a
pressure control cell at the end of each arm. The conditioning of
the pad can be done, but not limited, by replacing the wafer with a
conditioning disk with the same size as the wafer after every
operation.
[0033] Another example of the embodiments of the present invention
is using a single polish head and a wafer holder, as shown in FIG.
6. The positions of both of the polish head and the wafer can be
adjusted by adjusting levers in X and Y directions, respectively.
The detailed design of the two position adjusting levers is
schematically shown in FIG. 10 and 12. Combination of the two
adjustment levers make it possible for the polish head to reach any
die(s) desired to be polished on the wafer surface. The polish head
is connected with a motor, which is located in a container fixed to
the adjusting lever. The down force during polishing process can be
controlled by several pressure control cells inside the polish
head, which are shown in FIG. 7. The disk holding the pad, as shown
in FIG. 8, moves along a small orbit with radius 3-10 mm and
thereby the relative velocity between every point on the pad and
the polish are on the wafer surface is the same. The relative
velocity between the pad and the wafer can be adjusted by changing
the motor speed as well as the orbit radius. The orbital motion of
the pad can be achieved, but not limited, by a cam whose center has
an offset with the axle of the motor, as shown in FIG. 9. The wafer
holder, as shown in FIG. 10, can be changeable and with different
size for wafers with different size. Correspondingly, the position
adjustment levers for polish head as well as the wafer are also
changeable according to the requirement of the wafer size. But only
one polisher is used. The conditioning of the pad is achieved by a
separate conditioning disk that is located near the wafer holder
and its position can be given by the polish head adjusting lever
(FIG. 10). For blanket wafer, there are totally seven polish areas
on the wafer surface; for patterned wafer, there are as many as ten
polish areas. In this way, the wafer utilization is effectively and
efficiently improved. During the polishing process, only the polish
area on the wafer surface is open and the rest area is covered and
protected by a specifically designed mask. Also, a slurry
collection channel is given with the wafer holder to collect the
used slurry for further analysis. The tilting of the present
invention can be achieved, but not limited, by adjustable legs
whose heights can be adjusted to a required level.
[0034] In an embodiment of the present invention, a single arm can
have multiple types of pad, for example, a hard pad for copper
polishing and a soft pad for barrier polishing. There will be no
need to have multiple platens. A significant saving in space and
increase in throughput. As each individual die is polished
separately, there will be no cross contamination issue among dies.
The defect causing entity will be localized. There will be no
defect propagation like what usually happened on a conventional
polisher.
[0035] One variation on the polishing head is to replace the
conventional solid rigid pad with a softer more flexible polishing
tape as shown in FIG. 11. There are several advantages of using a
tape over polishing pad. A tape can be manufactured to contain
various chemical components such as soft abrasives, releasable
chemicals, surfactants, etc. The polishing performance can be
improved by the presence of these components in situ. It is much
easier to clean, purify, and reuse of a polishing tape. The
operation of a polisher that uses polishing tape can be more
automated and continuous. There are two further variations when a
polishing tape is used. One is to use a roller to hold and guide
the polishing tape. The down force and relative polishing speed is
determined by the lateral movement of the roller. As the absolute
contact area between the roller and the wafer is relatively small,
the rollers have to be moved laterally to increase the contact
surface area.
[0036] The rotation speed will be determined by the size of the
roller. For example, if a linear velocity of 1.0 m/sec is desired
and the diameter of a roller is 10 mm, the rotation speed should be
about 600 rpm. An alternative to the roller approach, a solid block
with a low friction surface can also be used to guide the tape
towards the wafer. The gap between the tape and the wafer can be
adjusted by a magnetic levitation current. A repulsive current can
create a actual gap between the tape and the wafer. This is
particularly useful for static and dynamic etch rate measurement
for slurry. An attractive current can exert the desired pressure
between the tape and the wafer. This down force can range from 0.01
psi to 10 psi. This is particularly useful for the polishing of a
wafer that uses soft and fragile low k dielectric materials.
Furthermore, the solid block can be replaced by a porous material
through which a positive air pressure can be applied. The porosity
of the material can lead to a small gap between the guiding block
and the tape. The gap between the block and the tape can eliminate
the complication created by the friction between them and give
closer contact between the tape and the wafer at microscopic
level.
[0037] Another variation of the invention is to use the said device
to evaluate slurry and its performance on a polishing process. One
example is illustrated in FIG. 12 in which a slurry chamber with
adjustable volume houses a carrier for polishing pad and a carrier
for wafer.
[0038] FIG. 12 shows a schematic of a slurry evaluator that can be
used to characterize polishing slurry for viscosity, friction upon
contact between a pad and a wafer in the presence of a slurry,
static etch rate with various fluid movements, and removal rate
upon contact between a pad and wafer and various low down forces.
The relative velocity and distance between the pad carrier and
wafer carrier are mechanically controlled and computer programmed
to vary during the polishing. The net averaging effect of these
variations is goal is to allow each location on the wafer to
experience the pad from all directions.
[0039] Both carriers are vertically positioned and can counter
rotate to each other at an adjustable rotation speed. Both carriers
can be driven by a simple DC motor with an effective seal to
prevent the interference of slurry. The lateral position of the
carrier for wafer is typically fixed. The lateral position of the
pad is adjustable. The adjustment can be accomplished with a second
motor that is connected to Motor A. A more desirable mechanism for
the control is through Magnetic Levitation Currents. Several
patents such as U.S. Pat. No. 6,750,625 teach the design and
application of magnetic levitation mechanism to control a stage in
a precision manor that matches the requirement for photolithography
(FIG. 13--A reproduction of work published by C. H. Meng and Z. P.
Zhang on the capability of a six axis magnetic levitation stage
designed for photolithographic application in the semiconductor
industry).
[0040] In addition patents such as U.S. Pat. No. 6,559,567 teach
the design and application of electromagnetic rotary drive. More
specifically, Schob et al teaches the use of senor arrangement in
an electromagnetic rotary device to measure the fluid property such
as viscosity (U.S. Pat. No. 6,355,998). In this inventive device,
an electromagnetic design can be implemented to control the lateral
and rotary movements of a pad carrier. When the pad and the wafer
are kept at far enough distance, the disturbance created by the pad
movement on the wafer film is minimal. The removal rate measured
under such condition can be considered as static etch rate or
something close. The resistance exerted on the movement of the pad
carrier is mainly due the slurry viscosity. When the distance
between the pad and wafer carrier is getting smaller, the
disturbance created by the pad movement on the wafer surface
significantly aids the transport of the fluid. The removal rate
measured under this circumstance should be viewed as a dynamic etch
rate. When the pad and wafer surfaces starts to make a contact, the
material removal on the wafer surface should increase
significantly. The material removal shall increase as the relative
pressure between the wafer and the pad increases. The removal rate
may eventually reach it plateau as shown in FIG. 14 (a reproduction
of a drawing published by Levitronix technique to measure viscosity
of a fluid (U.S. Pat. No. 6,640,617).
[0041] The initial slope and intercept describes the slurry's
static etch characteristics. The second slope and intercept
describes the slurry's polishing characteristics for the wafer
film. The combination of these two sets of information may provide
valuable insight about the planarization capability of this slurry.
This information can not be obtained directly with blanket wafer
with the current polishers.
[0042] The schematic of a polisher in FIG. 16 also show that uses
tape to replace polishing pad, the relative speed and location
between the tape center and die on the wafer are mechanically
controlled and computer programmed to vary during the polishing.
The net averaging effect of these variations is goal is to allow
each location on the wafer to experience the polishing tape from
all directions.
[0043] Other advantages of the present invention include but not
limited to: [0044] (1) Easy implementation of complete E-CMP. There
will be no electrical contact loss issues and thereby the
advantages of ECM can be fully utilized; [0045] (2) All types of
endpoint detection systems can be implemented. Unlike conventional
polisher, the implementation of optical, electrical, or frictional
endpoint detection system is easy. There will be no slurry
interference issues. Each die are will have its own endpoint
detection system. If a feedback loop control is present, there will
be no more need for over polishing as each die can stop polishing
as soon as it reaches to the endpoint. [0046] (3) For interlayer
dielectric polishing, it is desirable to have the global planarity
correction. While the wafer will still remain stationary, a single
orbital polisher wheel will come along. The unique design of this
polishing wheel will have the same linear velocity under the arm
for the majority of the area. When program properly, it should
reach global planarity with a single polish head. [0047] (4)
Greater productivity. There will be no down time due to pad
conditioning, pad change, and ex-situ conditioning of the pad.
During the change of wafers, the pads will be conditioned at the
same time. [0048] (5) The cost of the pad will be much less than
the cost in conventional polisher because of the small size of the
pad. Also, the within-pad non-uniformity due to conditioning is
eliminated.
[0049] And, the pad can be easily changed during wafer
switching.
[0050] The invention is further described by the following numbered
paragraphs: [0051] 1. A method of chemical mechanical polishing of
a surface of a substrate to remove selected portions thereof
comprising: [0052] (i) maintaining at least a portion of the
surface of the substrate in sliding fractional contact with the
polishing pad until the selected portions of the surface of the
substrate are removed; [0053] (ii) polishing one area on a
blanket/patterned wafer, containing one or more dies, using a
single polishing head with a small piece of commercial CMP pad or a
pad under evaluation; and [0054] (iii) polishing a patterned wafer
using multi-arm polishing head with each polishing arm
corresponding to a die on the patterned wafer. [0055] 2. The method
of paragraph 1, wherein the die(s) on the patterned wafer desired
to be polished is processed and the remaining dies are protected by
a cover or a mask. [0056] 3. The method of paragraph 1, wherein
only a portion of the surface of the substrate is polished by a
single polish head or multi-arm polish head with multiple pads
while the rest area of the surface of the substrate to be polished
is protected. [0057] 4. An apparatus for chemical mechanical
polishing of a surface of a substrate to remove selected portions
thereof comprising: [0058] (i) a fixed platen to hold the wafer to
be polished, the wafer holder is changeable, and the size of the
holder adjustable to fit different size of the wafer; [0059] (ii) a
cam with an offset with the motor axle to make orbital motion of
the polishing pad and achieves the same relative velocity between
each point on the pad and the area to be polished; [0060] (iii) a
device for providing an oscillatory motion on the surface of a
single die; [0061] (iv) a disk to hold the multi-arm polish head
system; [0062] (v) a slurry delivery system in which the slurry can
be supplied to each individual die on the patterned wafer
separately; [0063] (vi) a two-motor system, one motor rotates the
disk that holds the second motor and the second motor rotates the
pad in a same rotation speed and the same direction as that of the
first motor and thus the same relative velocity between each point
on the pad and the area to be polished is achieved; [0064] (vii) a
two-lever adjustment system to control the position of the polish
head and the wafer whereby all the dies on the patterned wafer can
be polished; [0065] (viii) adjustable legs for tilting the whole
apparatus; [0066] (ix) a slurry collection system to collect used
slurry; and [0067] (x) a replaceable pad conditioning disk. [0068]
5. The apparatus of paragraph 4, wherein the tubes of the slurry
delivery system are distributed in parallel. [0069] 6. A device for
the evaluation of the performance and characteristics of a slurry
comprising of a slurry chamber, a rotary wafer carrier that is
vertically placed and fixed on lateral movement, a rotary pad
carrier that is movable along its lateral axis, a sensor which
measures the film thickness change in-situ, and a sensor which
measures the resistance exerted on to the rotary movement of the
pad carrier. [0070] 7. The device of paragraph 6, lateral and
rotary movements for the pad and wafer carriers are accomplished by
DC motors. [0071] 8. The device of paragraph 6, lateral and rotary
movements of the pad carrier are accomplished by the use of a
magnetic levitation system. [0072] 9. The device of paragraph 6,
the film thickness change is measured by 14-point probe or Eddy
current system for metal films. [0073] 10. The device of paragraph
9, wherein the film is a dielectric film and the measurement is
made by an optical sensor. [0074] 11. The device of paragraph 10,
wherein an acoustic sensor for measuring the film thickness change
for metal and non-metal is simultaneously used. [0075] 12. A
polisher that utilizes polishing tape for IC wafer processing
comprising of a slurry delivery system, a tape management system, a
guiding system for the tape, and optionally a system for tape
cleaning, conditioning, and re-use. [0076] 13. The polisher of
paragraph 12, the tape can be made with natural, process natural
materials or synthetic materials. Processed natural materials
include but are not limited to silk, cotton and paper. The tape can
be made of entirely synthetic materials such as polyethylene,
polypropylene, and polystyrene. The tape materials can be
hydrophobic or hydrophilic. The materials can be made into porous
or non-porous. Furthermore, the tape can contain releasable
materials such as complexing agent, catalyst, surfactant,
lubricant, and/or abrasive particles. The tape can also contain
functional groups that can chemically interact with slurry and the
wafer film. [0077] 14. The polisher of paragraph 12, wherein the
tape management system may include but not limited to control the
tape tension, the tape movement, the tape cleaning, conditioning,
embossment of temporary patterns shortly before it reaches the
wafer, and a flipping mechanism that allows the use of either side
of the tape at will. [0078] 15. The polisher of paragraph 12,
wherein the tape guiding system may include a solid roller or a
block that controls the distance between the tape and the wafer.
When a solid block is used to guide the relative distance between
the wafer and the tape, the block may contain a magnetic material
that responses to levitation current which may create a gap between
the tape and the wafer. The electromagnetic current can also
control the relative pressure between the tape and wafer. In
another preferred embodiment, the guiding block can also be porous
and allow air stream to pass through. As a result, the exiting air
stream will create a small gap between the block and the tape. This
gap is adjustable.
[0079] It is to be understood that the present invention is capable
of use in various other combinations and is capable of changes and
modifications within the scope of the inventive concept as
expressed herein.
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