U.S. patent application number 11/962271 was filed with the patent office on 2008-04-24 for etching apparatus for semicondutor fabrication.
Invention is credited to Timothy J. Dalton, Emily F. Gallagher, Louis M. Kindt, Carey W. Thiel, Andrew J. Watts.
Application Number | 20080093342 11/962271 |
Document ID | / |
Family ID | 36930977 |
Filed Date | 2008-04-24 |
United States Patent
Application |
20080093342 |
Kind Code |
A1 |
Dalton; Timothy J. ; et
al. |
April 24, 2008 |
ETCHING APPARATUS FOR SEMICONDUTOR FABRICATION
Abstract
Method of operating an apparatus which allows etching different
substrate etch areas of a substrate having different pattern
densities at essentially the same etch rate. The apparatus includes
(a) a chamber; (b) an anode and a cathode in the chamber; and (c) a
bias power system coupled to the cathode, wherein the cathode
includes multiple cathode segments. The operation method is as
follows. A substrate to be etched is placed between the anode and
cathode, wherein the substrate includes N substrate etch areas, and
the N substrate etch areas are directly above the N cathode
segments. N bias powers are determined which when being applied to
the N cathode segments during an etching of the substrate, will
result in essentially a same etch rate for the N substrate etch
areas. Then, the bias power system is used to apply the N bias
powers the N cathode segments.
Inventors: |
Dalton; Timothy J.;
(Ridgefield, CT) ; Gallagher; Emily F.;
(Burlington, VT) ; Kindt; Louis M.; (Milton,
VT) ; Thiel; Carey W.; (Williston, VT) ;
Watts; Andrew J.; (Essex, VT) |
Correspondence
Address: |
SCHMEISER, OLSEN & WATTS
22 CENTURY HILL DRIVE
SUITE 302
LATHAM
NY
12110
US
|
Family ID: |
36930977 |
Appl. No.: |
11/962271 |
Filed: |
December 21, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10906627 |
Feb 28, 2005 |
|
|
|
11962271 |
Dec 21, 2007 |
|
|
|
Current U.S.
Class: |
216/71 |
Current CPC
Class: |
H01J 37/32091 20130101;
H01J 37/32541 20130101; H01J 37/32706 20130101 |
Class at
Publication: |
216/071 |
International
Class: |
C23F 1/00 20060101
C23F001/00 |
Claims
1. An apparatus operating method, comprising: providing (i) a
chamber, (ii) an anode and a cathode positioned in the chamber, and
(iii) a bias power system coupled to the cathode, wherein the
cathode comprises N cathode segments electrically insulated from
each other, N being an integer greater than 1; placing a substrate
to be etched between the anode and the cathode, wherein the
structure comprises N substrate etch areas facing the anode, and
wherein the N substrate etch areas are directly above the N cathode
segments in a reference direction and match in size and shape with
the N cathode segments, wherein the reference direction is
essentially perpendicular to a surface of the anode facing the
cathode; determining N bias powers which, when being applied
one-to-one to the N cathode segments during an etching of the
substrate, will result in essentially a same etch rate for the N
substrate etch areas; and using the bias power system to apply the
N bias powers one-to-one to the N cathode segments during the
etching of the substrate.
2. The method of claim 1, wherein said determining the N bias
powers comprises the steps of: (i) etching a first test substrate
using the steps (b) and (d), wherein the N bias powers are
predetermined; (ii) examining the first test substrate after step
(i) is performed; (iii) adjusting the N bias powers based on a
result of step (ii); and (iv) repeating steps (i), (ii) and (iii)
for at least one additional test substrate until step (ii) results
in essentially the same etch rate for the N substrate etch
areas.
3. The method of claim 1, wherein said determining the N bias
powers comprises: determining N pattern densities for the N
substrate etch areas; and using a database to determine the N bias
powers based on the N pattern densities, wherein the database
contains correlations between bias powers, pattern densities, and
etch rates.
4. The method of claim 3, wherein the correlations between bias
powers, pattern densities, and etch rates are determined from
empirical data.
5. The method of claim 1, wherein said using the bias power system
comprises using N bias power subsystems of the bias power system to
apply the N bias powers one-to-one to the N cathode segments,
wherein the N bias power subsystems are coupled one-to-one to the N
cathode segments.
6. The method of claim 1, wherein said using the bias power system
comprises: using a bias power subsystem of the bias power system to
generate a total bias power to an impedance dividing circuit of the
bias power system; and in response to the impedance dividing
circuit receiving the total bias power, using the impedance
dividing circuit to generate the N bias powers one-to-one to the N
cathode segments.
7. An apparatus operating method, comprising: providing (i) a
chamber, (ii) an anode and a cathode positioned in the chamber, and
(iii) a bias power system coupled to the cathode, wherein the
cathode comprises N cathode segments electrically insulated from
each other, N being an integer greater than 1; placing a substrate
to be etched between the anode and the cathode, wherein the
substrate comprises N substrate etch areas facing the anode, and
wherein the N substrate etch areas are directly above the N cathode
segments in a reference direction and match in size and shape with
the N cathode segments, wherein the reference direction is
essentially perpendicular to a surface of the anode facing the
cathode; applying a plasma generation power to the anode
sufficiently to generate a plasma in the chamber; and applying N
bias powers one-to-one to the N cathode segments.
8. The method of claim 7, wherein the N bias powers are such that N
substrate etch areas of the substrate experience essentially a same
etch rate.
9. The method of claim 7, wherein said applying the N bias powers
comprises using N bias power subsystems of the bias power system to
apply the N bias powers one-to-one to the N cathode segments,
wherein the N bias power subsystems are coupled one-to-one to the N
cathode segments.
10. The method of claim 7, wherein said applying the N bias powers
comprises: using a bias power subsystem of the bias power system to
generate a total bias power to an impedance dividing circuit of the
bias power system; and in response to the impedance dividing
circuit receiving the total bias power, using the impedance
dividing circuit to generate the N bias powers one-to-one to the N
cathode segments.
Description
[0001] This application is a divisional application claiming
priority to Ser. No. 10/906,627, filed Feb. 28, 2005.
BACKGROUND OF THE INVENTION
[0002] 1. Technical Field
[0003] The present invention relates to etching tools for
semiconductor and photomask fabrication, and more specifically, to
etching tools for dry etching.
[0004] 2. Related Art
[0005] A conventional fabrication process usually involves the step
of dry etching a top surface of a substrate (e.g., a wafer or a
photomask). Typically, first, a photoresist layer or any useful
masking layer can be applied to the substrate. Then, the mask layer
can be patterned using a photolithography process so that only
areas of substrate that need to be etched are exposed from
underneath the masking layer. The other areas of the substrate that
need to be kept intact are covered by the patterned masking layer.
Next, the substrate (with the patterned masking layer on top) can
be placed on the cathode of an etching chamber. A radio frequency
(RF, typically at a frequency of 0.1 MHz to 2.5 GHz) electrical
power generator can be applied to the anode of the chamber so as to
generate a plasma in the chamber. As a result, etchants generated
within the plasma chemically react with the exposed material of the
substrate surface to create a volatile product that can easily be
removed by the etch system. Thus the pattern of the patterned
masking layer is transferred to the substrate surface. Additional
RF electrical energy may be coupled into the cathode to both
increase the rate of etch processing and to provide directionality
to the reactive species generated within the plasma.
[0006] However, different substrate areas facing the anode may be
etched at different etch rates and with different profiles because
these different substrate areas may have different pattern
densities. The pattern density of a substrate can be defined as the
percentage of the exposed-to-atmosphere surface of the substrate.
For example, assume a 1 cm.sup.2 substrate consists of 0.4 cm.sup.2
being covered by the patterned mask layer and 0.6 cm.sup.2 being
exposed to the atmosphere. As the result, the pattern density of
the substrate to be etched is 60%. If a substrate consists of a
first substrate etch area with a higher pattern density than a
second substrate etch area, then the first substrate etch area
consumes etchants at a higher rate than the second substrate etch
area. As a result, fewer etchants are available for further etching
in the first substrate etch area than in the second substrate etch
area. Therefore, the etch rate (and other properties such as
feature profile) of the first substrate etch area is less than the
etch rate of the second substrate etch area.
[0007] As a result, there is a need for a new apparatus (and method
for operating the same) which allows etching different substrate
etch areas having different pattern densities at essentially the
same etch rate.
SUMMARY OF THE INVENTION
[0008] The present invention provides an apparatus, comprising (a)
a chamber; (b) an anode and a cathode positioned in the chamber;
and (c) a bias power system coupled to the cathode, wherein the
cathode comprises N cathode segments electrically insulated from
each other, N being an integer greater than 1, and wherein the bias
power system is configured to apply N bias powers one-to-one to the
N cathode segments.
[0009] The present invention also provides an apparatus operating
method, comprising the steps of (a) providing (i) a chamber, (ii)
an anode and a cathode positioned in the chamber, and (iii) a bias
power system coupled to the cathode, wherein the cathode comprises
N cathode segments electrically insulated from each other, N being
an integer greater than 1; (b) placing a substrate to be etched
between the anode and the cathode, wherein the structure comprises
N substrate etch areas facing the anode, and wherein the N
substrate etch areas are directly above the N cathode segments in a
reference direction and match in size and shape with the N cathode
segments, wherein the reference direction is essentially
perpendicular to a surface of the anode facing the cathode; (c)
determining N bias powers which, when being applied one-to-one to
the N cathode segments during an etching of the substrate, will
result in essentially a same etch rate for the N substrate etch
areas; and (d) using the bias power system to apply the N bias
powers one-to-one to the N cathode segments during the etching of
the substrate.
[0010] The present invention also provides an apparatus operating
method, comprising the steps of (a) providing (i) a chamber, (ii)
an anode and a cathode positioned in the chamber, and (iii) a bias
power system coupled to the cathode, wherein the cathode comprises
N cathode segments electrically insulated from each other, N being
an integer greater than 1; (b) placing a substrate to be etched
between the anode and the cathode, wherein the substrate comprises
N substrate etch areas facing the anode, and wherein the N
substrate etch areas are directly above the N cathode segments in a
reference direction and match in size and shape with the N cathode
segments, wherein the reference direction is essentially
perpendicular to a surface of the anode facing the cathode; (c)
applying a plasma generation power to the anode sufficiently to
generate a plasma in the chamber; and (d) applying N bias powers
one-to-one to the N cathode segments
[0011] The present invention also provides a new apparatus (and
method for operating the same) which allows etching different
substrate etch areas having different pattern densities at
essentially the same etch rate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 illustrates an apparatus, in accordance with
embodiments of the present invention.
[0013] FIG. 2 illustrates a plasma generation power system of the
apparatus of FIG. 1, in accordance with embodiments of the present
invention.
[0014] FIGS. 3A-3E illustrate different embodiments of a cathode of
the apparatus of FIG. 1.
[0015] FIGS. 4A-4B illustrate different embodiments of a bias power
system of the apparatus of FIG. 1.
[0016] FIG. 5 illustrates a bias power subsystem that can be used
in the embodiments of FIGS. 4A-4B, in accordance with embodiments
of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0017] FIG. 1 illustrates an apparatus 100, in accordance with
embodiments of the present invention. Illustratively, the apparatus
100 can comprise a chamber 110, an anode 120 and a cathode 130 in
the chamber 110. The chamber 110 can include a gas inlet 112 and a
gas outlet 114. The gas inlet 112 can be used to receive gas
species into the chamber 110. The gas outlet 114 can be used to
lead gases out of the chamber 110. The depiction and location of
gas inlet 112 and outlet 114 is purely representational in FIG. 1.
An actual inlet and outlet may consist of a plurality of actual
openings. Additionally, it is well known to one skilled in the arts
that the location of the inlet and outlet can be placed at
different locations within the chamber to modify the efficiency of
gas flow within the chamber and consequently the gas's influence on
a substrate placed within the chamber.
[0018] The anode 120 can be coupled to a plasma generation power
system 140. In one embodiment, the plasma generation power system
140 can be configured to generate a plasma generation power (e.g.,
a radio frequency voltage) to the anode 120 so as to create a
plasma from the gas species in the chamber 110. The plasma contains
etchants necessary for substrate etching.
[0019] The cathode 130 can comprise N cathode segments (not shown,
but details of these cathode segments will be described below)
matching in size and shape with N substrate etch areas (facing the
anode 120) of a substrate 160 placed on the cathode 130, wherein N
is an integer greater than one. The N cathode segments can be
electrically insulated from each other. The cathode 130 can be
coupled to a bias power system 150 which, during the etching of the
substrate 160, can be configured to generate N bias powers (e.g.,
each can be a radio frequency voltage) to the N cathode segments of
the cathode 130. By adjusting a bias power to a cathode segment,
the bias power system 150 can adjust the energy of the ions
bombarding the substrate etch area of the substrate 160 directly
above the cathode segment. As a result, by adjusting the bias power
to the cathode segment, the bias power system 150 can adjust the
etch rate for the substrate etch area directly above the cathode
segment.
[0020] In one embodiment, the N bias powers can be individually
assigned by prior assumptions or by theoretical calculations such
that when the N bias powers are applied one-to-one to the N cathode
segments during the dry etching of the substrate 160, the N
substrate etch areas experience essentially the same etch rate.
[0021] In another embodiment, the N bias powers can be individually
assigned by using a "design of experiments" methodology or a
simpler trial-and-error methodology. More specifically, multiple
substrates (not shown) identical to the substrate 160 can be etched
one after another using essentially the same etching settings (i.e.
pressure, etchants, gas flow rate, etc.) while individually varying
the N bias powers. The resultant substrates after etching can be
examined to determine the etch rate uniformity across the
substrate. Then the N bias powers can be individually adjusted
until the N substrate etch areas experience essentially the same
etch rate. In other words, the results of the etching of a
substrate can be used to determine new bias powers for etching the
next substrate, and so on until the etch result is satisfactory
(i.e., essentially the same etch rate for all the N substrate etch
areas).
[0022] Alternatively, the N bias powers can be individually
determined by using a database containing correlations between bias
powers, pattern densities, and etch rates. In one embodiment, the
database is built from empirical data. More specifically,
experiments (i.e., etching) can be carried out in a predetermined
etch setting (i.e., gas flow rate, etchants, pressures, etc.) for
different pattern densities and different applied bias powers, and
the resulting etch rates can be recorded and entered into the
database. To achieve essentially the same etch rate for all N
substrate etch areas with N given pattern densities in the
predetermined etch setting, the N bias powers can be individually
determined using the database.
[0023] FIG. 2 illustrates one embodiment of the plasma generation
power system 140 of the apparatus 100 of FIG. 1, in accordance with
embodiments of the present invention. Illustratively, the plasma
generation power system 140 can comprise (i) an RF (radio
frequency) power source 142, a matching network 144 coupled to the
RF power source 142, and, for a capacitively-coupled plasma source,
a blocking capacitor 146 coupling the matching network 144 to the
anode 120. For inductively-coupled plasma sources, blocking
capacitor 146 is optional. The RF power source 142 produces an
electrical voltage of the desired frequency. The matching network
144 matches the variable impedance of the plasma to the desired
fixed impedance of the RF power source 142 so as to maximize the
transfer of electrical power from RF power source 142 into the
chamber 110. Blocking capacitor 146 serves to prevent the flow of
direct current (DC) power from RF power source 142 into chamber
110, only allowing the passage of alternating current (AC)
power.
[0024] FIGS. 3A-3E illustrate different embodiments 130a, 130b,
130c, 130d, and 130e, respectively, of the cathode 130 of FIG. 1.
More specifically, FIG. 3A shows a top-down view of the cathode
130a. The cathode 130a can have the circular shape and can comprise
three cathode segments 130a1, 130a2, and 130a3. In one embodiment,
the cathode segments 130a1, 130a2, and 130a3 can be electrically
insulated from each other. In general, there can be N (N being an
integer greater than one) concentric cathode segments having ring
form as in FIG. 3A.
[0025] FIG. 3B shows a top-down view of the cathode 130b. The
cathode 130b can have the rectangular shape and can comprise four
(or any integer number greater than one) cathode segments 130b1,
130b2, 130b3, and 130b4. The cathode segments 130b1, 130b2, 130b3,
and 130b4 can be electrically insulated from each other.
[0026] FIG. 3C shows a top-down view of the cathode 130c. The
cathode 130b can have the rectangular shape and can comprise 12 (or
any integer number multiple of 4 and at least 4) cathode segments
of trapezoidal and triangular shapes. The cathode segments of the
cathode 130c can be electrically insulated from each other.
[0027] FIG. 3D shows a top-down view of the cathode 130d. The
cathode 130d can have the rectangular shape and can comprise
cathode segments arranged in 4 rows and 4 columns (i.e., 16 cathode
segments in total). In general, the number of rows and the number
of columns can be any positive integer (but can not be 1
simultaneously) and do not have to be the same. The cathode
segments of the cathode 130d can be electrically insulated from
each other.
[0028] FIG. 3E shows a top-down view of the cathode 130e. The
cathode 130e can have the circular shape and can comprise cathode
segments arranged in 7 rows and 7 columns (i.e., 49 cathode
segments in total). In general, the number of rows and the number
of columns can be any positive integer (but can not be 1
simultaneously) and do not have to be the same. The cathode
segments of the cathode 130e can be electrically insulated from
each other.
[0029] In general, the cathode 130 of FIG. 1 can have any shape and
can comprise any number (more specifically, any integer greater
than 1) of cathode segments. Each of the cathode segments can have
any size and shape.
[0030] FIGS. 4A-4B illustrate two different embodiments 150a and
150b, respectively, of the bias power system 150 of FIG. 1. More
specifically, with reference to FIG. 4A, assume the cathode
embodiment 130a of FIG. 3A is used as the cathode 130 of FIG. 1 (in
FIG. 4A, a cross-section view of the cathode 130a is shown).
Because the cathode 130a has three cathode segments 130a1, 130a2,
and 130a3, the bias power system 150a can comprise the same number
of (i.e., three) independent bias power subsystems 150a1, 150a2,
and 150a3 coupled one-to-one to the cathode segments 130a1, 130a2,
and 130a3, respectively. The three bias power subsystems 150a1,
150a2, and 150a3 can be configured to generate three independent
bias powers (e.g., radio frequency voltages) one-to-one to the
three cathode segments 130a1, 130a2, and 130a3, respectively.
[0031] In general, if the cathode 130 of FIG. 1 has M cathode
segments (M being an integer greater than 1), then M bias power
subsystems similar to the bias power subsystems 150a1, 150a2, and
150a3 of can be used to generate M independent bias powers
one-to-one to the M cathode segments.
[0032] With reference to FIG. 4B, assume the cathode embodiment
130a of FIG. 3A is again used as the cathode 130 of FIG. 1 (in FIG.
4B, a cross-section view of the cathode 130a is shown). In one
embodiment, the bias power system 150b can comprise a bias power
subsystem 150b' and an impedance dividing circuit 152 coupling the
bias power subsystem 150b' to the cathode segments 130a1, 130a2,
and 130a3. The bias power subsystem 150b' can be configured to
generate a total bias power to the impedance dividing circuit 152.
In response to receiving the total bias power from the bias power
subsystem 150b', the impedance dividing circuit 152 can be
configured to generate three different bias powers one-to-one to
the three cathode segments 130a1, 130a2, and 130a3.
[0033] The simplest example of an impedance divider circuit is a
voltage divider circuit. In this case, an input voltage is put
through two resistors (fixed or variable) in series. The output
voltage is taken off between the two resistors.
[0034] In general, a series of M voltage dividers may be
constructed to drive M cathode segments. By applying the same input
voltage to each of the M voltage dividers, the output to each of
the M cathode segments can be individually adjusted.
[0035] FIG. 5 illustrates a bias power subsystem 500 that can be
used as the bias power subsystems 150a1, 150a2, and 150a3 of FIG.
4A and the bias power subsystems 150b' of FIG. 4B. In one
embodiment, the bias power subsystem 500 can comprise (i) an RF
power source 502, a matching network 504 coupled to the RF power
source 502, and, for a capacitively-coupled plasma source, a
blocking capacitor 506 coupling the matching network 504 either to
the cathode 130a of FIG. 4A or to the impedance dividing circuit
152 of FIG. 4B. For inductively-coupled plasma sources, blocking
capacitor 506 is optional. Generator 502 produces an electrical
voltage at the desired frequency. Matching network 504 matches the
variable impedance of the plasma across the substrate 160 (FIG. 1)
to the desired fixed impedance of generator 502 so as to maximize
the transfer of electrical power from generator 502 into substrate
160 (FIG. 1). Blocking capacitor 506 serves to prevent the flow of
direct current (DC) power from generator 502 into substrate 160 and
chamber 110 (FIG. 1), only allowing the passage of alternating
current (AC) power. Modulation of the output of generator 502
produces a modulation in the bias voltage on substrate 160 (FIG.
1).
[0036] In summary, with reference to FIG. 1, by using the N-segment
cathode 130, N bias powers can be individually determined such that
when these N bias powers are applied to the N cathode segments (not
shown), the N substrate etch areas of the substrate 160 directly
above the N cathode segments experience essentially the same etch
rate. The N bias powers can be individually determined by trials
and errors, or alternatively, by using a database built through
experiments.
[0037] In a similar manner, the present invention can be used to
etch a variety of substrates 160 (FIG. 1). For example, the present
invention can be used to etch a wafer or a photomask.
[0038] While particular embodiments of the present invention have
been described herein for purposes of illustration, many
modifications and changes will become apparent to those skilled in
the art. Accordingly, the appended claims are intended to encompass
all such modifications and changes as fall within the true spirit
and scope of this invention.
* * * * *