U.S. patent application number 13/233960 was filed with the patent office on 2012-08-30 for cmp apparatus, polishing pad and cmp method.
Invention is credited to Akifumi GAWASE, Yukiteru Matsui.
Application Number | 20120220195 13/233960 |
Document ID | / |
Family ID | 46719302 |
Filed Date | 2012-08-30 |
United States Patent
Application |
20120220195 |
Kind Code |
A1 |
GAWASE; Akifumi ; et
al. |
August 30, 2012 |
CMP APPARATUS, POLISHING PAD AND CMP METHOD
Abstract
According to one embodiment, a CMP apparatus includes a
supplying portion supplying a slurry to a surface portion of a
polishing pad including water-soluble particles, a holding portion
contacting an object to be polished with the surface portion of the
polishing pad in a condition of holding the object, a temperature
setting portion on the surface portion of the polishing pad, the
temperature setting portion setting a temperature of the surface of
the polishing pad. A control portion executes a first polishing
step and a second polishing step after the first polishing step,
the object is polished in a condition of setting the temperature of
the surface of the polishing pad within a first temperature range
in the first polishing step, and the object is polished in a
condition of setting the temperature of the surface of the
polishing pad within a second temperature range in the second
polishing step.
Inventors: |
GAWASE; Akifumi;
(Yokohama-shi, JP) ; Matsui; Yukiteru;
(Yokohama-shi, JP) |
Family ID: |
46719302 |
Appl. No.: |
13/233960 |
Filed: |
September 15, 2011 |
Current U.S.
Class: |
451/7 |
Current CPC
Class: |
B24B 37/015 20130101;
B24B 37/24 20130101 |
Class at
Publication: |
451/7 |
International
Class: |
B24B 51/00 20060101
B24B051/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 25, 2011 |
JP |
2011-040468 |
Claims
1. A CMP apparatus comprising: a supplying portion supplying a
slurry to a surface portion of a polishing pad including
water-soluble particles; a holding portion contacting an object to
be polished with the surface portion of the polishing pad in a
condition of holding the object; a temperature setting portion on
the surface portion of the polishing pad, the temperature setting
portion setting a temperature of the surface of the polishing pad;
and a control portion controlling an operation of the supplying
portion, the holding portion and the temperature setting portion,
wherein the control portion executes a first polishing step and a
second polishing step after the first polishing step, the object is
polished in a condition of setting the temperature of the surface
of the polishing pad within a first temperature range in the first
polishing step, and the object is polished in a condition of
setting the temperature of the surface of the polishing pad within
a second temperature range in the second polishing step.
2. The apparatus of claim 1, wherein the control portion controls
an operation of the temperature setting portion based on a
dissolved threshold value at which the water-soluble particles
completely dissolve into the slurry.
3. The apparatus of claim 1, wherein a solubility of the
water-soluble particles exposed to the surface portion of the
polishing pad in the second polishing step is higher than the
solubility of the water-soluble particles exposed to the surface
portion of the polishing pad in the first polishing step.
4. The apparatus of claim 3, wherein the solubility of the
water-soluble particles is controlled by causing the slurry
supplied to the surface portion of the polishing pad from the
supplying portion to contain a substance that is the same as the
water-soluble particles or has the same property as the
water-soluble particles in advance.
5. The apparatus of claim 1, further comprising a stage portion on
which the polishing pad is mounted, wherein the holding portion and
the stage portion are driven to rotate, and the control portion
monitors a torque current value used to drive the holding portion
or the stage portion to rotate and changes the first polishing step
to the second polishing step after the torque current value is
judged to have passed through a first change point.
6. The apparatus of claim 5, further comprising a surface
conditioning portion that conditions a state of the surface portion
of the polishing pad, wherein the control portion terminates the
second polishing step after the torque current value is judged to
have passed through a second change point and executes a surface
conditioning step for returning the surface portion of the
polishing pad to an initial state by the surface conditioning
portion after the temperature of the surface portion of the
polishing pad is changed from within the second temperature range
to within the first temperature range.
7. The apparatus of claim 1, wherein the temperature setting
portion includes a heat exchanger in contact with the surface
portion of the polishing pad.
8. The apparatus of claim 1, wherein the temperature setting
portion includes a mechanism that supplies an inert gas to the
surface portion of the polishing pad.
9. The apparatus of claim 1, wherein the temperature setting
portion includes a mechanism to cool the surface portion of the
polishing pad and the temperature of the surface portion of the
polishing pad is controlled by frictional heat between the
polishing pad and the object to be polished and the mechanism.
10. The apparatus of claim 9, wherein the temperature of the
surface portion of the polishing pad changes linearly.
11. The apparatus of claim 1, wherein the water-soluble particles
are dextrin or cellulose containing an aliphatic chain.
12. A polishing pad using the apparatus of claim 1, comprising: a
water-insoluble crosslinked polymer; and water-soluble particles in
the crosslinked polymer, wherein a solubility of the water-soluble
particles changes during polishing of an object to be polished.
13. A CMP method comprising: supplying slurry to a surface portion
of a polishing pad including water-soluble particles; bringing an
object to be polished into contact with the surface portion of the
polishing pad; and executing a first polishing step and a second
polishing step after the first polishing step, the object being
polished in a condition of setting the temperature of the surface
portion of the polishing pad within a first temperature range in
the first polishing step, and the object being polished in a
condition of setting the temperature of the surface portion of the
polishing pad within a second temperature range in the second
polishing step.
14. The method of claim 13, wherein a solubility of the
water-soluble particles exposed to the surface portion of the
polishing pad in the second polishing step is higher than a
solubility of the water-soluble particles exposed to the surface
portion of the polishing pad in the first polishing step.
15. The method of claim 13, wherein a solubility of the
water-soluble particles is controlled by causing the slurry
supplied to the surface portion of the polishing pad from the
supplying portion to contain a substance that is the same as the
water-soluble particles or has the same property as the
water-soluble particles in advance.
16. The method of claim 13, wherein the object to be polished and
the polishing pad are driven to rotate, and a torque current value
at which the object to be polished or the polishing pad is driven
to rotate is monitored and the first polishing step is changed to
the second polishing step after the torque current value is judged
to have passed through a first change point.
17. The method of claim 16, wherein polishing of the object to be
polished is terminated after the torque current value is judged to
have passed through a second change point, and the surface portion
of the polishing pad is returned to an initial state after the
temperature of the surface portion of the polishing pad is changed
from within the second temperature range to within the first
temperature range.
18. The method of claim 13, wherein the temperature of the surface
portion of the polishing pad is set by a heat exchanger in contact
with the surface portion of the polishing pad.
19. The method of claim 13, wherein the temperature of the surface
portion of the polishing pad is set by a mechanism that supplies an
inert gas to the surface portion of the polishing pad.
20. The method of claim 13, wherein the temperature of the surface
portion of the polishing pad is set by frictional heat between the
polishing pad and the object to be polished and a mechanism to cool
the surface portion of the polishing pad.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from prior Japanese Patent Application No. 2011-040468,
filed Feb. 25, 2011, the entire contents of which are incorporated
herein by reference.
FIELD
[0002] Embodiments described herein relate generally to a CMP
apparatus, a polishing pad and a CMP method.
BACKGROUND
[0003] In semiconductor processes, Chemical Mechanical Polishing
(CMP) is used to planarize a dielectric film, metal film,
polysilicon film and the like embedded in a groove. In
next-generation devices of the 32-nm generation or thereafter, it
is necessary to ensure a high level of flatness and reduce
polishing scratches at the same time in the CMP step to reduce
focus errors and improve yields in an exposure step accompanying
micropatterning.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIGS. 1 and 2 are diagrams showing a CMP apparatus;
[0005] FIG. 3 is a diagram showing a polishing pad;
[0006] FIG. 4 is a diagram showing an object to be polished;
[0007] FIG. 5 is a diagram showing a management table;
[0008] FIG. 6 is a diagram showing a change in torque current
value;
[0009] FIG. 7 is a flowchart showing a first example of an
operation of the CMP apparatus;
[0010] FIG. 8 is a diagram showing a temperature change in a
surface portion of the polishing pad;
[0011] FIGS. 9 to 12 are diagrams showing a CMP method;
[0012] FIG. 13 is a diagram showing the object to be polished in a
first polishing step;
[0013] FIG. 14 is a diagram showing the object to be polished in a
second polishing step;
[0014] FIG. 15 is a diagram showing the object to be polished when
the second polishing step is finished;
[0015] FIG. 16 is a diagram showing elasticity in a CMP step;
[0016] FIG. 17 is a flowchart showing a second example of the
operation of the CMP apparatus;
[0017] FIG. 18 is a diagram showing the temperature change in the
surface portion of the polishing pad;
[0018] FIGS. 19 to 22 are diagrams showing the CMP method;
[0019] FIG. 23 is a diagram showing a modification of the CMP
apparatus;
[0020] FIG. 24 is a flowchart showing a third example of the
operation of the CMP apparatus;
[0021] FIG. 25 is a diagram showing the temperature change in the
surface portion of the polishing pad;
[0022] FIG. 26 is a diagram showing the CMP method; and
[0023] FIGS. 27 to 29 are diagrams showing the CMP method.
DETAILED DESCRIPTION
[0024] In general, according to one embodiment, a CMP apparatus
comprising: a supplying portion supplying a slurry to a surface
portion of a polishing pad including water-soluble particles; a
holding portion contacting an object to be polished with the
surface portion of the polishing pad in a condition of holding the
object; a temperature setting portion on the surface portion of the
polishing pad, the temperature setting portion setting a
temperature of the surface of the polishing pad; and a control
portion controlling an operation of the supplying portion, the
holding portion and the temperature setting portion, wherein the
control portion executes a first polishing step and a second
polishing step after the first polishing step, the object is
polished in a condition of setting the temperature of the surface
of the polishing pad within a first temperature range in the first
polishing step, and the object is polished in a condition of
setting the temperature of the surface of the polishing pad within
a second temperature range in the second polishing step.
[0025] The embodiment relates to, for example, a CMP apparatus, a
polishing pad, and a CMP method used in a planarization process in
a method of manufacturing a semiconductor device. In the
planarization process, ensuring a high level of flatness and
reducing polishing scratches of a dielectric film, metal film,
polysilicon film and so on embedded in a groove poses a
challenge.
[0026] However, flatness and polishing scratches have a correlation
with elasticity of the polishing pad. For example, increased
elasticity of the polishing pad leads to improved flatness and
increased polishing scratches. Conversely, decreased elasticity of
the polishing pad leads to decreased polishing scratches and
degraded flatness. Regarding polishing scratches, however, there is
a strong correlation with elasticity particularly near the surface
of the polishing pad.
[0027] To improve this trade-off, a polishing pad containing
water-soluble particles is developed. According to this technology,
a state of high elasticity in an inner portion of the polishing pad
that is not exposed to water and low elasticity in a surface
portion that is exposed to water is realized. However, the surface
portion of the polishing pad always has low elasticity during
polishing of an object to be polished according to this technology,
which is not sufficient for a device requiring an ultrahigh level
of flatness.
[0028] Also, a technology to control elasticity of a whole
polishing pad during a CMP process by installing piping for cooling
the polishing pad inside the polishing pad or on the back side of
the polishing pad to control the temperature of the entire
polishing pad is developed. However, it is not possible to control
elasticity of only the surface portion of the polishing pad
according to this technology, which is not sufficient for the above
tradeoff.
[0029] Thus, the embodiment proposes a polishing pad containing
water-soluble particles whose solubility is controlled and a CMP
apparatus including a mechanism capable of controlling the
temperature of the polishing pad.
[0030] That is, a CMP apparatus in the embodiment is used together
with a polishing pad containing water-soluble particles as a pair.
Moreover, a temperature setting portion to set the temperature of
the surface portion of the polishing pad is provided in the surface
portion of the polishing pad. Then, polishing of an object to be
polished is performed while the temperature of the surface portion
of the polishing pad is set to within a first temperature range and
then, polishing of the object to be polished is performed while the
temperature of the surface portion of the polishing pad is set to
within a second temperature range.
[0031] Accordingly, the polishing pad containing water-soluble
particles is in two states during polishing of the object to be
polished. The first state arises when the temperature of the
surface portion of the polishing pad is within the first
temperature range and is a state in which elasticity of the entire
polishing pad is high. The second state arises when the temperature
of the surface portion of the polishing pad is within the second
temperature range and is a state in which elasticity of the surface
portion of the polishing pad is low and elasticity of portions
other than the surface portion is high.
[0032] In the first state, a solubility of water-soluble particles
exposed to the surface portion of the polishing pad is reduced to
0% or a low state and thus, elasticity of the entire polishing pad
is high. Therefore, polishing with importance placed on ensuring a
high level of flatness is performed on the object to be
polished.
[0033] In the first state, the solubility of water-soluble
particles exposed to the surface portion of the polishing pad is
desirably 10% or less from the viewpoint of ensuring a high level
of flatness.
[0034] In the second state, the solubility of water-soluble
particles exposed to the surface portion of the polishing pad is
high and thus, elasticity of the surface portion of the polishing
pad is low. In portions other than the surface portion, elasticity
is high because water-soluble particles are not exposed and are not
dissolved. Therefore, polishing with importance placed on the
reduction of polishing scratches on the object to be polished is
performed.
[0035] The second state is realized by controlling elasticity of
only the surface portion of the polishing pad and thus, elasticity
of portions other than the surface portion of the polishing pad
remains high and flatness is not degraded by the polishing.
[0036] By causing these two states during polishing of the object
to be polished, it becomes possible to ensure a high level of
flatness and reduce polishing scratches at the same time.
[0037] The solubility of water-soluble particles exposed to the
surface portion of the polishing pad can be controlled by, in
addition to the temperature of the surface portion of the polishing
pad, causing slurry (for example, containing polishing particles
and water) supplied to the surface portion of the polishing pad to
contain a substance that is the same as water-soluble particles or
has the same property as water-soluble particles in advance.
[0038] FIGS. 1 and 2 show a CMP apparatus as an embodiment.
[0039] FIG. 1 is a perspective view of a CMP apparatus and FIG. 2
is a side view of the CMP apparatus in FIG. 1.
[0040] Stage portion (for example, rotating table) 11 is, for
example, driven to rotate (clockwise/counterclockwise). Polishing
pad 12 containing water-soluble particles is mounted on stage
portion 11.
[0041] Polishing pad 12 is configured by, for example, as shown in
FIG. 3, water-insoluble crosslinked polymer 12a. Crosslinked
polymer 12a is a foam and is filled with water-soluble particles
12b. Such polishing pad 12 is called a filler pad.
[0042] A crosslinked polymer is polyurethane, polystyrene or the
like and water-soluble particles are a polysaccaride such as
dextrin, cellulose containing an aliphatic chain or the like.
[0043] Holding portion 13 holds object to be polished 14 and brings
object to be polished 14 into contact with the surface portion of
polishing pad 12 while holding object to be polished 14. Holding
portion 13 is, for example, driven to rotate
(clockwise/counterclockwise).
[0044] Stage portion 11 and holding portion 13 are desirably driven
to rotate together from the viewpoint of eliminating unevenness of
the polishing amount of object to be polished 14. When both are
driven to rotate, the rotation direction of holding portion 13 and
the rotation direction of stage portion 11 are desirably the
same.
[0045] Object to be polished 14 is, for example, as shown in FIG.
4, a semiconductor device. Here, a semiconductor device including
semiconductor substrate 14a, stopper film 14b on semiconductor
substrate 14a, and dielectric film 14c embedded in a groove of
semiconductor substrate 14a is shown as an example of object to be
polished 14.
[0046] In FIG. 4, stopper film 14b is formed of a material having
etching selectivity to dielectric film 14c. If, for example,
dielectric film 14c is a silicon oxide film, stopper film 14b is a
silicon nitride film.
[0047] Supplying portion 15 is arranged above stage portion 11 and,
if stage portion 11 is, for example, cylindrical, above the center
portion of a circle to supply slurry to the surface portion of
polishing pad 12. The slurry contains, for example, a chemical
solution such as a polishing agent, water and the like.
[0048] By causing the slurry to contain a substance that is the
same as water-soluble particles or has the same property as
water-soluble particles in advance, the solubility of water-soluble
particles exposed to the surface portion of polishing pad 12 can be
controlled. Being able to control the solubility of water-soluble
particles means also increasing choices of water-soluble
particles.
[0049] Further, if a polysaccaride such as dextrin is used as
water-soluble particles, the solubility thereof into the slurry can
be adjusted by adjusting the molecular weight thereof.
[0050] Surface conditioning portion 16 has a function to, by
polishing object to be polished 14, return the surface portion of
polishing pad 12 worn out or clogged by abrasive grains contained
in the polishing agent or the like to the initial state of object
to be polished 14 before polishing.
[0051] In the present example, water-soluble particles exposed to
the surface portion of polishing pad 12 are dissolved by one CMP
step on object to be polished 14 and thus, surface conditioning
portion 16 returns the surface portion of polishing pad 12 to the
initial state each time the one CMP step ends.
[0052] Surface conditioning portion 16 returns the surface portion
of polishing pad 12 to the initial state by cutting a fixed amount
of the surface portion of polishing pad 12 to expose new
water-soluble particles to the surface portion of polishing pad
12.
[0053] Temperature setting portion 17 is arranged in the surface
portion of polishing pad 12 to set the temperature of the surface
portion of polishing pad 12. Temperature setting portion 17
includes, for example, a heat exchanger (contact mechanism) that
comes into contact with the surface portion of polishing pad 12 and
a non-contact mechanism that supplies an inert gas (heat-exchanger
gas) to the surface portion of polishing pad 12.
[0054] If temperature setting portion 17 is configured by a heat
exchanger, the controllable temperature range of the surface
portion of the polishing pad can be ensured widely, increasing
choices of the type of polishing pad (water-soluble particles) 12.
If temperature setting portion 17 is configured by a non-contact
mechanism, scratches and non-uniformity will not be caused in
polishing pad 12 and, as a result, polishing scratches of object to
be polished 14 can further be reduced.
[0055] Temperature setting portion 17 may further include a
temperature sensor. Alternatively, temperature setting portion 17
may not include a temperature sensor by providing the temperature
sensor in a portion other than temperature setting portion 17.
[0056] Control portion 18 controls operations of stage portion 11,
holding portion 13, supplying portion 15, surface conditioning
portion 16, and temperature setting portion 17. Control portion 18
sets the temperature of the surface portion of polishing pad 12
through temperature setting portion 17 based on a dissolved
threshold value at which water-soluble particles exposed to the
surface portion inside polishing pad 12 can completely be
dissolved.
[0057] If the temperature of the surface portion of the polishing
pad is set to the dissolved threshold value or higher under the
assumption that water-soluble particles can dissolve into slurry
without limitation, the solubility of water-soluble particles
exposed to the surface portion in polishing pad 12 becomes
100%.
[0058] However, if the slurry contains a substance that is the same
as water-soluble particles or has the same property as
water-soluble particles in advance, a saturated state may be
reached before water-soluble particles are completely dissolved so
that the solubility of water-soluble particles exposed to the
surface portion in polishing pad 12 may be less than 100% even if
the temperature of the surface portion inside polishing pad 12 is
equal to or higher than the dissolved threshold value.
[0059] Control portion 18 includes management table 19 to set the
temperature of the surface portion of polishing pad 12 through
temperature setting portion 17 based on the dissolved threshold
value.
[0060] Management table 19 includes, for example, as shown in FIG.
5, information about the slurry, polishing pad, and dissolved
threshold value of water-soluble particles and control portion 18
is caused to store management table 19 therein in advance. For
example, the slurry and polishing pad are freely exchangeable and
thus, input information about the slurry and polishing pad is input
into control portion 18 before driving a CMP apparatus in the
present example.
[0061] Based on the input information, control portion 18
recognizes the dissolved threshold value to realize the above two
states during polishing of object to be polished 14.
[0062] Management table 19 is only an example and if, for example,
one of the slurry and polishing pad is fixed, only unfixed
information may be input to decide the dissolved threshold value.
Alternatively, the dissolved threshold value of water-soluble
particles may directly be input into control portion 18 without
providing management table 19.
[0063] Control portion 18 also includes torque current monitor
portion 20.
[0064] Torque current monitor portion 20 is provided to decide a
switching point of a first polishing step in the first state in
which entire polishing pad 12 has high elasticity, a second
polishing step in the second state in which only the surface
portion of polishing pad 12 has low elasticity, and further a
surface conditioning step of polishing pad 12 in which the surface
portion of polishing pad 12 is returned to the initial state.
[0065] That is, when stage portion 11 and holding portion 13 are
each driven at a fixed rotation speed, the switching point can be
decided by monitoring a torque current value to drive stage portion
11 and holding portion 13 to rotate.
[0066] If object to be polished 14 is, for example, a semiconductor
device shown in FIG. 4, the above first polishing step can be
executed while irregularities of dielectric film 14c are present
and the above second polishing step can be executed while
irregularities of dielectric film 14c are eliminated.
[0067] This is because, for example, as shown in FIG. 6, the torque
current value increases due to contact resistance between polishing
pad 12 and object to be polished 14 with decreasing irregularities
of dielectric film 14c and after irregularities of dielectric film
14c are eliminated, the torque current value becomes constant at
the maximum value. Therefore, the first polishing step can be
switched to the second polishing step by detecting change point
(first change point) P1 of the torque current value.
[0068] The above second polishing step can be executed while
irregularities of dielectric film 14c are eliminated and the CMP
step can be finished to execute the above surface conditioning step
while stopper film 14b is exposed.
[0069] This is because the contact resistance between polishing pad
12 and dielectric film 14c and the contact resistance between
polishing pad 12 and stopper film 14b are different. Therefore, for
example, as shown in FIG. 6, the second polishing step can be
switched to the surface conditioning step by detecting change point
(second change point) P2 of the torque current value.
[0070] To detect change points P1, P2 of the torque current value,
for example, a fixed judgment term is necessary and thus, it is
desirable to switch each step after this judgment term.
[0071] Installation of torque current monitor portion 20 is
desirable to switch the first polishing step, second polishing
step, and surface conditioning step correctly.
[0072] However, these steps can be switched without providing
torque current monitor portion 20. For example, the first polishing
step, second polishing step, and surface conditioning step may be
switched by monitoring the polishing time in the CMP step according
to a rule of thumb.
[0073] FIG. 7 shows a first example of the CMP method.
[0074] This flowchart is executed by control portion 18 in FIG.
1.
[0075] Water-soluble particles in the polishing pad are a substance
whose solubility into slurry increases with a rising temperature
within the temperature range of the surface portion of the
polishing pad set by the temperature setting portion.
[0076] It is assumed that dissolved threshold value (temperature)
Tc1 of water-soluble particles is within the temperature range
thereof and water-soluble particles exposed to the surface portion
of the polishing pad can completely dissolve into slurry when the
temperature of the surface portion inside the polishing pad is
equal to or higher than dissolved threshold value Tc1.
[0077] Under the above assumption, for example, as shown in FIG. 8,
the temperature of the surface portion of the polishing pad is
changed. That is, in the first polishing step, the temperature of
the surface portion of the polishing pad is made sufficiently lower
than dissolved threshold value Tc1. In the second polishing step,
the temperature of the surface portion of the polishing pad is made
equal to or higher than dissolved threshold value Tc1. Further, in
the surface conditioning step of the polishing pad, the temperature
of the surface portion of the polishing pad is made sufficiently
lower than dissolved threshold value Tc1 again.
[0078] Concrete operations will be described below based on the
flowchart in FIG. 7 and side views in FIGS. 9 to 15.
[0079] First, dissolved threshold value Tc1 is set to a register in
the control portion based on input information (for example, the
slurry, polishing pad and so on) (step ST1).
[0080] After, as shown in FIG. 9, stage portion 11 on which
polishing pad 12 is mounted is rotated, slurry is supplied onto
polishing pad 12 from supplying portion 15. The slurry is spread
over entire polishing pad 12 due to a centrifugal force.
[0081] Subsequently, temperature Tsurface of the surface portion of
polishing pad 12 is set to the first temperature range (less than
dissolved threshold value Tc1) (step ST2).
[0082] Then, as shown in FIG. 10, object to be polished 14 held by
holding portion 13 is brought into contact with polishing pad 12 to
execute the first polishing step to polish object to be polished 14
while temperature Tsurface of the surface portion of polishing pad
12 is maintained within the first temperature range. At this point,
like stage portion 11, holding portion 13 may also be rotated.
[0083] In the first polishing step, temperature Tsurface of the
surface portion of polishing pad 12 is set to within the first
temperature range and thus, the solubility of water-soluble
particles exposed to the surface portion of polishing pad 12 into
slurry is 0% or a low state (desirably 10% or less).
[0084] Therefore, elasticity of entire polishing pad 12 is
maintained high and polishing with importance placed on maintenance
of a high level of flatness is performed. Also, as shown in FIG.
13, a protrusion of dielectric film 14c of object to be polished 14
mainly comes into contact with polishing pad 12 to be
preferentially polished. Therefore, when the first polishing step
proceeds to some extent, irregularities of dielectric film 14c of
object to be polished 14 are eliminated.
[0085] Then, after, as shown in FIG. 14, the surface of dielectric
film 14c of object to be polished 14 is planarized, a contact area
(contact resistance) between polishing pad 12 and object to be
polished 14 increases, causing a change of the torque current value
(first change point P1 in FIG. 6).
[0086] The torque current monitor portion monitors torque current
value Itorque during a CMP step and after passing through change
point (first change point) P1, switches the first polishing step to
the second polishing step (step ST3).
[0087] That is, the torque current monitor portion sets temperature
Tsurface of the surface portion of polishing pad 12 to the second
temperature range (dissolved threshold value Tc1 or higher) (step
ST4).
[0088] Then, as shown in FIG. 11, the second polishing step to
polish object to be polished 14 is subsequently executed while
temperature Tsurface of the surface portion of polishing pad 12 is
maintained within the second temperature range.
[0089] In the second polishing step, temperature Tsurface of the
surface portion of polishing pad 12 is set to within the second
temperature range and thus, the solubility of water-soluble
particles exposed to the surface portion of polishing pad 12 into
slurry is high (100% or close thereto).
[0090] The solubility of water-soluble particles in the second
polishing step has only to be higher than that of water-soluble
particles in the first polishing step. That is, it is desirable to
adjust the solubility of water-soluble particles in the second
polishing step in accordance with the type of object to be polished
14.
[0091] Therefore, elasticity of the surface portion of polishing
pad 12 is maintained low and polishing with importance placed on
the reduction of polishing scratches is performed. Elasticity of
portions other than the surface portion of polishing pad 12 remains
high and a high level of flatness is not degraded by the second
polishing step.
[0092] The second polishing step is desirably as short as possible
on condition that the amount and size of polishing scratches are
within permissible ranges.
[0093] As shown in FIG. 15, when the second polishing step proceeds
to some extent, the surface of stopper film 14b of object to be
polished 14 is exposed.
[0094] If the surface of stopper film 14b of object to be polished
14 is exposed, the contact resistance between polishing pad 12 and
object to be polished 14 changes and thus, a change in torque
current value also appears (second change point P2 in FIG. 6).
[0095] The torque current monitor portion monitors torque current
value Itorque during a CMP step and after passing through change
point (second change point) P2, terminates the second polishing
step (step ST5).
[0096] Then, as shown in FIG. 12, holding portion 13 is raised to
move object to be polished 14 away from polishing pad 12. Also, the
surface conditioning step to return the surface portion of
polishing pad 12 to the initial state is executed while temperature
Tsurface of the surface portion of polishing pad 12 is maintained
within the first temperature range (less than dissolved threshold
value Tc1).
[0097] That is, while temperature Tsurface of the surface portion
of polishing pad 12 is set to within the first temperature range
(step ST6), surface conditioning portion 16 is lowered and the
surface portion of polishing pad 12 is cut by surface conditioning
portion 16 to newly expose water-soluble particles to the surface
portion of polishing pad 12 (step ST7).
[0098] The temperature of polishing pad 12 does not change markedly
in the surface conditioning step, but it is necessary to pay close
attention to the temperature of polishing pad 12 so that the
temperature does not rise to Tc1 or higher.
[0099] According to the present example (embodiment), as shown in
FIG. 16, elasticity of polishing pad 12 changes during a CMP step.
Moreover, the first state in which elasticity of entire polishing
pad 12 is high is maintained in the first polishing step and the
second state in which elasticity of only the surface portion of
polishing pad 12 is lowered from the first state is maintained in
the second polishing step.
[0100] Therefore, according to the embodiment, compared with
Comparative Example 1 in which elasticity is constant during CMP
step and Comparative Example 2 in which elasticity of the entire
polishing pad changes during CMP step, both of ensuring a high
level of flatness and the reduction of polishing scratches can be
improved.
[0101] FIG. 17 shows a second example of the CMP method.
[0102] This flowchart is executed by control portion 18 in FIG.
1.
[0103] Water-soluble particles in the polishing pad are a substance
whose solubility into slurry increases with a falling temperature
within the temperature range of the surface portion of the
polishing pad set by the temperature setting portion.
[0104] It is assumed that dissolved threshold value (temperature)
Tc2 of water-soluble particles is within the temperature range
thereof and water-soluble particles exposed to the surface portion
of the polishing pad can completely dissolve into slurry when the
temperature of the surface portion inside the polishing pad is
equal to or lower than dissolved threshold value Tc2.
[0105] Under the above assumption, for example, as shown in FIG.
18, the temperature of the surface portion of the polishing pad is
changed. That is, in the first polishing step, the temperature of
the surface portion of the polishing pad is made sufficiently
higher than dissolved threshold value Tc2. In the second polishing
step, the temperature of the surface portion of the polishing pad
is made equal to or lower than dissolved threshold value Tc2.
Further, in the surface conditioning step of the polishing pad, the
temperature of the surface portion of the polishing pad is made
sufficiently higher than dissolved threshold value Tc2 again.
[0106] Concrete operations will be described below based on the
flowchart in FIG. 17 and side views in FIGS. 19 to 22.
[0107] First, dissolved threshold value Tc2 is set to a register in
the control portion based on input information (for example, the
slurry, polishing pad and so on) (step ST1).
[0108] After, as shown in FIG. 19, stage portion 11 on which
polishing pad 12 is mounted is rotated, slurry is supplied onto
polishing pad 12 from supplying portion 15. The slurry is spread
over entire polishing pad 12 due to a centrifugal force.
[0109] Subsequently, temperature Tsurface of the surface portion of
polishing pad 12 is set to the first temperature range (exceeding
dissolved threshold value Tc2) (step ST2).
[0110] Then, as shown in FIG. 20, object to be polished 14 held by
holding portion 13 is brought into contact with polishing pad 12 to
execute the first polishing step to polish object to be polished 14
while temperature Tsurface of the surface portion of polishing pad
12 is maintained within the first temperature range. At this point,
like stage portion 11, holding portion 13 may also be rotated.
[0111] In the first polishing step, temperature Tsurface of the
surface portion of polishing pad 12 is set to within the first
temperature range and thus, the solubility of water-soluble
particles exposed to the surface portion of polishing pad 12 into
slurry is 0%, or low (desirably 10% or less).
[0112] Therefore, elasticity of entire polishing pad 12 is
maintained high and polishing with importance placed on maintenance
of a high level of flatness is performed. Also, as shown in FIG.
13, a protrusion of dielectric film 14c of object to be polished 14
mainly comes into contact with polishing pad 12 to be
preferentially polished. Therefore, when the first polishing step
proceeds to some extent, irregularities of dielectric film 14c of
object to be polished 14 are eliminated.
[0113] Then, after, as shown in FIG. 14, the surface of dielectric
film 14c of object to be polished 14 is planarized, a contact area
(contact resistance) between polishing pad 12 and object to be
polished 14 increases, causing a change of the torque current value
(first change point P1 in FIG. 6).
[0114] The torque current monitor portion monitors torque current
value Itorque during CMP step and after passing through change
point (first change point) P1, switches the first polishing step to
the second polishing step (step ST3).
[0115] That is, temperature Tsurface of the surface portion of
polishing pad 12 is set to the second temperature range (dissolved
threshold value Tc2 or lower) (step ST4).
[0116] Then, as shown in FIG. 21, the second polishing step to
polish object to be polished 14 is subsequently executed while
temperature Tsurface of the surface portion of polishing pad 12 is
maintained within the second temperature range.
[0117] In the second polishing step, temperature Tsurface of the
surface portion of polishing pad 12 is set to within the second
temperature range and thus, the solubility of water-soluble
particles exposed to the surface portion of polishing pad 12 into
slurry is high (100% or close thereto).
[0118] The solubility of water-soluble particles in the second
polishing step has only to be higher than that of water-soluble
particles in the first polishing step. That is, it is desirable to
adjust the solubility of water-soluble particles in the second
polishing step in accordance with the type of object to be polished
14.
[0119] Therefore, elasticity of the surface portion of polishing
pad 12 is maintained low and polishing with importance placed on
the reduction of polishing scratches is performed. Elasticity of
other portions than the surface portion of polishing pad 12 remains
high and a high level of flatness is not degraded by the second
polishing step.
[0120] The second polishing step is desirably as short as possible
on condition that the amount and size of scratches are within
permissible ranges.
[0121] As shown in FIG. 15, when the second polishing step proceeds
to some extent, the surface of stopper film 14b of object to be
polished 14 is exposed.
[0122] If the surface of stopper film 14b of object to be polished
14 is exposed, the contact resistance between polishing pad 12 and
object to be polished 14 changes and thus, a change in torque
current value also appears (second change point P2 in FIG. 6).
[0123] The torque current monitor portion monitors torque current
value Itorque during CMP step and after passing through change
point (second change point) P2, terminates the second polishing
step (step ST5).
[0124] Then, as shown in FIG. 22, holding portion 13 is raised to
move object to be polished 14 away from polishing pad 12. Also, the
surface conditioning step to return the surface portion of
polishing pad 12 to the initial state is executed while temperature
Tsurface of the surface portion of polishing pad 12 is maintained
within the first temperature range (exceeding dissolved threshold
value Tc2).
[0125] That is, while temperature Tsurface of the surface portion
of polishing pad 12 is set to within the first temperature range
(step ST6), surface conditioning portion 16 is lowered and the
surface portion of polishing pad 12 is cut by surface conditioning
portion 16 to newly expose water-soluble particles to the surface
portion of polishing pad 12 (step ST7).
[0126] The temperature of polishing pad 12 does not change markedly
in the surface conditioning step, but it is necessary to pay close
attention to the temperature of polishing pad 12 so that the
temperature does not fall to Tc2 or lower.
[0127] According to the present example (embodiment), as shown in
FIG. 16, elasticity of polishing pad 12 changes during a CMP step.
Moreover, the first state in which elasticity of entire polishing
pad 12 is high is maintained in the first polishing step and the
second state in which elasticity of only the surface portion of
polishing pad 12 is lowered from the first state is maintained in
the second polishing step.
[0128] Therefore, according to the embodiment, compared with
Comparative Example 1 in which elasticity is constant during a CMP
step and Comparative Example 2 in which elasticity of the entire
polishing pad changes during a CMP step, both of ensuring a high
level of flatness and the reduction of polishing scratches can be
improved.
[0129] FIG. 23 shows a modification of the CMP apparatus in FIG.
1.
[0130] This modification is different from the CMP apparatus in
FIG. 1 in that temperature setting portion 21 includes only a
cooling mechanism and omits a heating mechanism.
[0131] This is because frictional heat is generated between
polishing pad 12 and object to be polished 14 during CMP step. The
temperature of polishing pad 12 gradually rises due to frictional
heat without being heated by temperature setting portion 21. By
using this frictional heat, the heating mechanism can be omitted to
simplify the configuration of temperature setting portion 21.
[0132] The cooling mechanism includes, for example, a heat
exchanger (contact mechanism) that comes into contact with the
surface portion of polishing pad 12 and a non-contact mechanism
that supplies an inert gas (heat-exchanger gas) to the surface
portion of polishing pad 12. If the cooling mechanism is configured
by a non-contact mechanism, scratches and non-uniformity will not
be caused in polishing pad 12 and, as a result, polishing scratches
of object to be polished 14 can further be reduced.
[0133] However, if this example is adopted, it is necessary to
verify how frictional heat generated between polishing pad 12 and
object to be polished 14 changes during a CMP step in advance.
[0134] That is, the necessary condition is that before executing
the second polishing step, the temperature of the surface portion
of polishing pad 12 is the dissolved threshold value or higher.
[0135] Other structural elements are the same as those of the CMP
apparatus in FIG. 1 and a detailed description thereof is
omitted.
[0136] FIG. 24 shows a third example of the CMP method.
[0137] This flowchart is executed by control portion 18 in FIG.
23.
[0138] Water-soluble particles in the polishing pad are a substance
whose solubility into slurry increases with a rising temperature
within the temperature range of the surface portion of the
polishing pad set by the temperature setting portion.
[0139] It is assumed that dissolved threshold value (temperature)
Tc3 of water-soluble particles is within the temperature range
thereof and water-soluble particles exposed to the surface portion
of the polishing pad can completely dissolve into slurry when the
temperature of the surface portion inside the polishing pad is
equal to or higher than dissolved threshold value Tc3.
[0140] Under the above assumption, the temperature of the surface
portion of the polishing pad changes, for example, as shown in FIG.
25, linearly due to frictional heat between the polishing pad and
the object to be polished.
[0141] That is, the temperature of the surface portion of the
polishing pad gradually rises in the first polishing step due to
frictional heat, but does not reach dissolved threshold value
Tc3.
[0142] In the second polishing step, the temperature of the surface
portion of the polishing pad is maintained at dissolved threshold
value Tc3 or higher due to frictional heat. However, it is
desirable to control the temperature of the surface portion of the
polishing pad so that the temperature is stabilized to a certain
value equal to or higher than dissolved threshold value Tc3 to
avoid too high a temperature by frictional heat and cooling by the
temperature setting portion.
[0143] Further, in the surface conditioning step of the polishing
pad, the temperature of the surface portion of the polishing pad is
set to less than dissolved threshold value Tc3 by cooling of the
temperature setting portion.
[0144] Concrete operations will be described below based on the
flowchart in FIG. 24 and side views in FIGS. 26 to 29.
[0145] First, dissolved threshold value Tc3 is set to a register in
the control portion based on input information (for example, the
slurry, polishing pad and so on) (step ST1).
[0146] After, as shown in FIG. 26, stage portion 11 on which
polishing pad 12 is mounted is rotated, slurry is supplied onto
polishing pad 12 from supplying portion 15. The slurry is spread
over entire polishing pad 12 due to a centrifugal force.
[0147] At this point, temperature (initial value) Tsurface of the
surface portion of polishing pad 12 is assumed to be within the
first temperature range (less than dissolved threshold value
Tc3).
[0148] Subsequently, as shown in FIG. 27, object to be polished 14
held by holding portion 13 is brought into contact with polishing
pad 12 to execute the first polishing step to polish object to be
polished 14. At this point, like stage portion 11, holding portion
13 may also be rotated.
[0149] In the first polishing step, temperature Tsurface of the
surface portion of polishing pad 12 gradually rises due to
frictional heat. However, temperature Tsurface will not reach
dissolved threshold value Tc3 or higher if the relationship between
the time and temperature rise rate is controlled by the cooling
mechanism of the temperature setting portion (step ST2).
[0150] Therefore, the solubility of water-soluble particles exposed
to the surface portion of polishing pad 12 into slurry is 0% or low
(desirably 10% or less).
[0151] Therefore, elasticity of entire polishing pad 12 is
maintained high and polishing with importance placed on maintenance
of a high level of flatness is performed. Also, as shown in FIG.
13, a protrusion of dielectric film 14c of object to be polished 14
mainly comes into contact with polishing pad 12 to be
preferentially polished. Therefore, when the first polishing step
proceeds to some extent, irregularities of dielectric film 14c of
object to be polished 14 are eliminated.
[0152] Then, after, as shown in FIG. 14, the surface of dielectric
film 14c of object to be polished 14 is planarized, a contact area
(contact resistance) between polishing pad 12 and object to be
polished 14 increases, causing a change of the torque current value
(first change point P1 in FIG. 6).
[0153] The torque current monitor portion monitors torque current
value Itorque during a CMP step and after passing through change
point (first change point) P1, switches the first polishing step to
the second polishing step (step ST3).
[0154] That is, temperature Tsurface of the surface portion of
polishing pad 12 is set to the second temperature range (dissolved
threshold value Tc3) by increasing the temperature rise rate of the
surface portion of polishing pad 12 at a stroke through frictional
heat by weakening the cooling mechanism or making the cooling
mechanism inoperable (step ST4).
[0155] Then, as shown in FIG. 28, the second polishing step to
polish object to be polished 14 is subsequently executed while
temperature Tsurface of the surface portion of polishing pad 12 is
maintained within the second temperature range by frictional heat
and the cooling mechanism.
[0156] In the second polishing step, temperature Tsurface of the
surface portion of polishing pad 12 is set to within the second
temperature range and thus, the solubility of water-soluble
particles exposed to the surface portion of polishing pad 12 into
slurry is high (100% or close thereto).
[0157] The solubility of water-soluble particles in the second
polishing step has only to be higher than that of water-soluble
particles in the first polishing step. That is, it is desirable to
adjust the solubility of water-soluble particles in the second
polishing step in accordance with the type of object to be polished
14.
[0158] Therefore, elasticity of the surface portion of polishing
pad 12 is maintained low and polishing with importance placed on
the reduction of polishing scratches is performed. Elasticity of
other portions than the surface portion of polishing pad 12 remains
high and a high level of flatness is not degraded by the second
polishing step.
[0159] The second polishing step is desirably as short as possible
on condition that the amount and size of scratches are within
permissible ranges.
[0160] As shown in FIG. 15, when the second polishing step proceeds
to some extent, the surface of stopper film 14b of object to be
polished 14 is exposed.
[0161] If the surface of stopper film 14b of object to be polished
14 is exposed, the contact resistance between polishing pad 12 and
object to be polished 14 changes and thus, a change in torque
current value also appears (second change point P2 in FIG. 6).
[0162] The torque current monitor portion monitors torque current
value Itorque during a CMP step and after passing through change
point (second change point) P2, terminates the second polishing
step (step ST5).
[0163] Then, as shown in FIG. 29, holding portion 13 is raised to
move object to be polished 14 away from polishing pad 12. Also, the
surface conditioning step to return the surface portion of
polishing pad 12 to the initial state is executed while temperature
Tsurface of the surface portion of polishing pad 12 is set to
within the first temperature range (less than dissolved threshold
value Tc3) by the cooling mechanism.
[0164] That is, while temperature Tsurface of the surface portion
of polishing pad 12 is maintained within the first temperature
range (step ST6), surface conditioning portion 16 is lowered and
the surface portion of polishing pad 12 is cut by surface
conditioning portion 16 to newly expose water-soluble particles to
the surface portion of polishing pad 12 (step ST7).
[0165] The temperature of polishing pad 12 does not change markedly
in the surface conditioning step, but it is necessary to pay close
attention to the temperature of polishing pad 12 so that the
temperature does not rise to Tc3 or higher.
[0166] According to the present example (embodiment), as shown in
FIG. 16, elasticity of polishing pad 12 changes during a CMP step.
Moreover, the first state in which elasticity of entire polishing
pad 12 is high is maintained in the first polishing step and the
second state in which elasticity of only the surface portion of
polishing pad 12 is lowered from the first state is maintained in
the second polishing step.
[0167] Therefore, according to the embodiment, compared with
Comparative Example 1 in which elasticity is constant during a CMP
step and Comparative Example 2 in which elasticity of the entire
polishing pad changes during a CMP step, both of ensuring a high
level of flatness and the reduction of polishing scratches can be
improved.
[0168] According to the embodiment, a CMP technology capable of
ensuring a high level of flatness and reducing polishing scratches
can be provided. Therefore, highly reliable semiconductor devices
can be manufactured by applying the technology to manufacturing
processes of next-generation devices of the 32-nm generation or
thereafter or devices of novel structures having a wide space.
Next-Generation Devices
[0169] Next-generation devices such as a resistance changing memory
(for example, a resistive random access memory: ReRAM) attempt to
increase the memory capacity by making a memory cell array
three-dimensional. To realize such a memory cell array
(three-dimensional cross-point type) of next-generation devices, a
CMP technology that ensures a high level of flatness and reduces
polishing scratches at the same time is indispensable. Therefore,
application of the embodiment makes next-generation devices
realizable.
Devices of Novel Structures
[0170] In recent years, many devices having novel structures that
are micropatterened and multi-layered have been developed. By
applying the CMP technology in the embodiment to such devices, a
highly reliable semiconductor device can be realized. In a device
of a novel structure, for example, it is difficult to impose
constraints according to conventional design rules and ensuring a
high level of flatness of dielectric films embedded in a wide space
is also important along with embedding of fine spaces. Therefore,
application of the embodiment makes such devices of novel
structures realizable.
[0171] While certain embodiments have been described, these
embodiments have been presented by way of example only, and are not
intended to limit the scope of the inventions. Indeed, the novel
embodiments described herein may be embodied in a variety of other
forms; furthermore, various omissions, substitutions and changes in
the form of the embodiments described herein may be made without
departing from the spirit of the inventions. The accompanying
claims and their equivalents are intended to cover such forms or
modifications as would fall within the scope and spirit of the
inventions.
* * * * *