U.S. patent application number 13/076272 was filed with the patent office on 2012-10-04 for increasing masking layer etch rate and selectivity.
This patent application is currently assigned to TOKYO ELECTRON LIMITED. Invention is credited to IAN J. BROWN, WALLACE P. PRINTZ.
Application Number | 20120248061 13/076272 |
Document ID | / |
Family ID | 46925858 |
Filed Date | 2012-10-04 |
United States Patent
Application |
20120248061 |
Kind Code |
A1 |
BROWN; IAN J. ; et
al. |
October 4, 2012 |
INCREASING MASKING LAYER ETCH RATE AND SELECTIVITY
Abstract
Provided is a method and system for increasing etch rate and
etch selectivity of a masking layer on a substrate, wherein the
system comprises a plurality of substrates containing the masking
layer and a layer of silicon or silicon oxide, an etch processing
chamber configured to process the plurality of substrates, the
processing chamber containing a treatment liquid for etching the
masking layer, and a boiling apparatus coupled to the processing
chamber and configured to generate a supply of steam water vapor
mixture at elevated pressure, wherein the steam water vapor mixture
is introduced into the processing chamber at a controlled rate to
maintain a selected target etch rate and a target etch selectivity
ratio of the masking layer to silicon or silicon oxide.
Inventors: |
BROWN; IAN J.; (AUSTIN,
TX) ; PRINTZ; WALLACE P.; (AUSTIN, TX) |
Assignee: |
TOKYO ELECTRON LIMITED
TOKYO
JP
|
Family ID: |
46925858 |
Appl. No.: |
13/076272 |
Filed: |
March 30, 2011 |
Current U.S.
Class: |
216/12 ;
156/345.11 |
Current CPC
Class: |
H01L 21/67253 20130101;
H01L 22/12 20130101; H01L 21/31111 20130101; H01L 21/6708 20130101;
C09K 13/04 20130101; H01L 21/67086 20130101; H01L 21/30612
20130101 |
Class at
Publication: |
216/12 ;
156/345.11 |
International
Class: |
C23F 1/02 20060101
C23F001/02; C23F 1/16 20060101 C23F001/16; C23F 1/08 20060101
C23F001/08 |
Claims
1. A system for increasing etch rate and etch selectivity of a
masking layer on a substrate, the system comprising: a plurality of
substrates containing the masking layer and a layer of silicon or
silicon oxide; an etch processing chamber configured to process the
plurality of substrates, the etch processing chamber containing a
treatment liquid for etching the masking layer in the plurality of
substrates; and a boiling apparatus coupled to the processing
chamber and configured to generate a supply of steam water vapor
mixture at elevated pressure; wherein the steam water vapor mixture
is introduced into the etch processing chamber at a flow rate
sufficient to maintain a selected target etch rate and a selected
target etch selectivity ratio of the masking layer to silicon or
silicon oxide.
2. The system of claim 1, where the masking layer comprises one of
silicon nitride, gallium nitride, or aluminum nitride.
3. The system of claim 2, wherein the treatment liquid is an
aqueous phosphoric acid solution.
4. The system of claim 2, wherein the selected target etch
selectivity ratio is in the range from 10:1 to 1000:1.
5. The system of claim 3, wherein a temperature of the aqueous
phosphoric acid solution is in the range of 160 to 220 degrees
Centigrade.
6. The system of claim 2, wherein the steam water vapor mixture at
elevated pressure and a treatment liquid are combined at high
pressure prior to entering the etch processing chamber.
7. The system of claim 2, wherein the steam water vapor mixture at
elevated pressure and a treatment liquid are combined at high
pressure prior to exiting supply delivery lines to the etch
processing chamber.
8. The system of claim 2, wherein: the flow rate and pressure of
the steam water vapor mixture are controlled to maintain the
selected target etch rate and the selected target etch selectivity
ratio of silicon nitride to silicon or silicon oxide.
9. The system of claim 1, wherein: the steam water vapor mixture at
elevated pressure is introduced into the etch processing chamber
using nozzles fitted along a bottom and a side of the etch
processing chamber; and the steam water vapor mixture is introduced
at a controlled rate to maintain the selected target etch rate and
the selected target etch selectivity ratio of the masking layer to
silicon or silicon oxide.
10. The system of claim 1, wherein the treatment liquid includes
one of phosphoric acid, hydrofluoric acid, or hydrofluoric
acid/ethylene glycol.
11. The system of claim 1 wherein the flow rate and pressure of the
steam water vapor mixture are controlled to cause a temperature of
the treatment liquid, causing in turn a boiling point temperature
of the treatment liquid and further causing an equilibrium
concentration and temperature of the treatment liquid to achieve
the target etch rate and the target etch selectivity ratio.
12. A method of increasing etch rate and etch selectivity of a
masking layer on a substrate, the method comprising: fabricating a
plurality of substrates containing the masking layer and a layer of
silicon or silicon oxide; obtaining a supply of steam water vapor
mixture at an elevated pressure; obtaining a supply of a treatment
liquid for selectively etching the masking layer over the silicon
or silicon oxide at a set etch rate and a set etch selectivity
ratio; placing the plurality of substrates into an etch processing
chamber; combining the treatment liquid and the steam water vapor
mixture; and injecting the combined treatment liquid and the steam
water vapor mixture into the etch processing chamber; wherein a
flow of the combined treatment liquid and the steam water vapor
mixture is configured to maintain the set etch rate and the set
etch selectivity ratio of the masking layer to silicon or silicon
oxide.
13. The method of claim 12, where the masking layer comprises
silicon nitride.
14. The method of claim 13, wherein the treatment liquid comprises
an aqueous phosphoric acid solution.
15. The method of claim 13, wherein the set etch selectivity ratio
is from 10:1 to 1000:1.
16. The method of claim 13, wherein a temperature of the aqueous
phosphoric acid solution is in the range of 160 to 180 degrees
Centigrade.
17. The method of claim 13, wherein the steam water vapor mixture
at elevated pressure and the treatment liquid are combined at high
pressure prior to entering the etch processing chamber.
18. The method of claim 13, wherein: the injecting the combined
treatment liquid and the steam water vapor mixture uses nozzles
fitted along a bottom and/or sides of the etch processing chamber;
and the steam water vapor mixture is introduced at a controlled
rate to maintain the set etch selectivity ratio of silicon nitride
to silicon or silicon oxide.
19. The method of claim 13, wherein the treatment liquid includes
one of phosphoric acid, hydrofluoric acid, or hydrofluoric
acid/ethylene glycol.
20. The method of claim 19, wherein the masking layer includes one
of silicon nitride, gallium nitride, or aluminum nitride.
21. The method of claim 20 wherein flow rate and pressure of the
steam water vapor mixture are controlled to cause a temperature of
the treatment liquid, causing in turn a boiling point temperature
of the treatment liquid and further causing an equilibrium
concentration and temperature of the treatment liquid to achieve
the target etch rate and the target etch selectivity ratio.
22. A method of increasing etch rate and selectivity of etching
silicon nitride on a substrate, the method comprising: placing a
plurality of substrates containing a masking layer of silicon
nitride and a layer of silicon or silicon oxide into an etch
processing chamber; combining a treatment liquid and a steam water
vapor mixture under elevated pressure; and injecting the combined
treatment liquid and the steam water vapor mixture into the etch
processing chamber; wherein a flow of the combined treatment liquid
and the steam water vapor mixture are controlled to maintain a
target etch rate of the silicon nitride and a target etch
selectivity ratio of the silicon nitride to silicon or silicon
oxide.
23. The method of claim 22, wherein the treatment liquid includes
one of phosphoric acid, hydrofluoric acid, or hydrofluoric
acid/ethylene glycol.
24. The method of claim 23 wherein a flow rate and pressure of the
steam water vapor mixture are controlled to cause a temperature of
the treatment liquid, causing in turn a boiling point temperature
and further causing an equilibrium concentration and temperature of
the treatment liquid to achieve the target etch rate and the target
etch selectivity ratio.
Description
BACKGROUND
[0001] 1. Field
[0002] The present application generally relates to the design of
an etch treatment system and method for increasing etch rate and
selectivity of etching a masking layer using a batch etch
process.
[0003] 2. Related Art
[0004] Current methods in the production of complementary metal
oxide semiconductor (CMOS) transistors require masking layers to
separate and protect active device regions such as dielectric,
metal interconnect, strain, source/drain, and the like. Silicon
nitride (Si.sub.3N.sub.4) or silicon oxide (SiO.sub.x, wherein x is
greater than 0) is often used as a masking layer due to its
electrical and morphological similarity to silicon dioxide
(SiO.sub.2), as well as because silicon nitride is easily bonded to
SiO.sub.2. Generally, silicon nitride is used as an etch-stop layer
but in certain cases, such as in a "dual damascene" process, the
silicon nitride must be etched away without altering the
carefully-controlled thickness of the silicon dioxide underlayer.
In such instances, the etch selectivity of silicon nitride to
silicon oxide, calculated as the etch rate of silicon nitride
divided by the etch rate of silicon oxide, ideally is as high as
possible to improve the process margin. As devices continue to
shrink, the thickness of masking layers and underlayers shrink in
tandem. Etch selectivity for ultra-thin layers will become more of
a challenge in the future.
[0005] Current techniques for selectively etching silicon nitride
may use differing chemistries and approaches. Both dry-plasma
etching as well as aqueous-chemistry etch are used in the removal
of silicon nitride. Aqueous chemistry materials can include dilute
hydrofluoric Acid (dHF), hydrofluoric acid/ethylene glycol as well
as phosphoric acid. The decision for using the different
chemistries is governed by the requirement for silicon nitride etch
rate and selectivity to oxide. Aqueous chemistry methods are
preferable because of the reduced cost of ownership compared to dry
techniques. It is well understood the silicon nitride etch rate in
phosphoric acid is strongly influenced by temperature, where the
etch rate rises in response to a rise in temperature. In a
wet-bench configuration such as immersing substrates into a bath of
aqueous phosphoric acid solution, the process temperature is
limited by the boiling point of the aqueous phosphoric acid
solution. The boiling point of the solution is a function of the
concentration of water in aqueous phosphoric acid solution as well
as the atmospheric pressure. One current method for maintaining
temperature is by a feedback-loop-controller that measures the
existence of a boiling state, while adjusting the addition of water
volume and heater power timing interval to the bath so as to
maintain this boiling state at a target temperature, (typical range
of target temperatures is from 140 degrees Centigrade to 160
degrees Centigrade). When the aqueous phosphoric acid solution is
heated without addition of water, the boiling point of the aqueous
phosphoric acid solution rises as the water is evaporated from the
solution.
[0006] Increasing the temperature of the phosphoric acid is
favorable for increasing the silicon nitride etch rate for
production and lower the cost of manufacturing at the expense of
lower selectivity because with current phosphoric acid
recirculation tanks, the consequence of allowing a high boiling
point is to reduce the concentration of water. Water is critical in
controlling the selectivity of silicon nitride to silicon oxide or
silicon etching. Experimental evidence shows that a non-boiling
state (i.e., low water content) at elevated temperature does not
result in a favorable etch selectivity. Conversely, to improve
selectivity, it would be preferable to have a high concentration of
water, (i.e., dilute the acid further), however this is not
practical. Increasing the concentration of water in the bath
reduces the boiling point of the acid mixture. At lower
temperature, the etch rate of the silicon nitride falls
significantly due to the strong Arrhenius relationship of the
silicon nitride etch rate with temperature.
[0007] In the current art, for example, Morris, in U.S. Pat. No.
4,092,211, discloses a method for controlling within a boiling
aqueous phosphoric acid solution the etch rate of a silicon oxide
insulator layer which is employed in masking a silicon nitride
insulator layer. The method employs the deliberate addition of a
silicate material to the boiling aqueous phosphoric acid solution.
In addition, Bell et al., in U.S. Pat. No. 5,332,145, disclose a
method for continuously monitoring and controlling the compositions
of low-solids soldering fluxes that employ a solvent with a
specific gravity closely matched to the specific gravity of the
flux composition. Desirable in the art are methods and systems that
can maintain a high etch rate for a masking layer and also maintain
a high selectivity of etching the masking layer over the silicon or
silicon oxide. There is a need for batch etch treatment systems and
methods and single substrate systems and methods that can meet the
goals of etch rate, etch selectivity, etch time, and/or cost of
ownership.
SUMMARY
[0008] Provided is a method and system for increasing etch rate and
etch selectivity of a masking layer on a substrate, wherein the
system comprises a plurality of substrates containing the masking
layer and a layer of silicon or silicon oxide, an etch processing
chamber configured to process the plurality of substrates, the
processing chamber containing a treatment liquid for etching the
masking layer, and a boiling apparatus coupled to the processing
chamber and configured to generate a supply of steam water vapor
mixture at elevated pressure, wherein the steam water vapor mixture
is introduced into the processing chamber at a controlled rate to
maintain a selected target etch rate and a selected target etch
selectivity ratio of the masking layer to silicon or silicon
oxide.
BRIEF DESCRIPTION OF DRAWINGS
[0009] FIG. 1 is an architectural diagram illustrating prior art
method of etching silicon nitride in a batch etch process.
[0010] FIG. 2 depicts an exemplary architectural diagram
illustrating a prior art batch etch treatment system using a water
supply and heaters for etching silicon nitride.
[0011] FIG. 3 depicts an exemplary graph of the boiling point of
phosphoric acid as a function of phosphoric acid concentration and
temperature.
[0012] FIG. 4A is an exemplary graph of the boiling point of
phosphoric acid as a function of phosphoric acid concentration and
temperature and an exemplary graph of steam pressure as a function
of temperature for mixture equilibrium conditions in an etch
treatment system.
[0013] FIG. 4B is an exemplary graph of the boiling point of
phosphoric acid as a function of phosphoric acid concentration and
temperature and an exemplary graph of steam pressure as a function
of temperature for mixture equilibrium conditions at two steam
pressures in an etch treatment system.
[0014] FIG. 5A depicts an exemplary graph of the composition of
phosphoric acid solutions as a function of temperature.
[0015] FIG. 5B depicts an exemplary graph of etch selectivity of
phosphoric acid solutions as a function of time and temperature in
an etch treatment system.
[0016] FIG. 6A depicts an exemplary schematic representation of
batch etch treatment system according to an embodiment of the
present invention.
[0017] FIG. 6B depicts an exemplary schematic representation of a
single substrate etch treatment system according to an embodiment
of the present invention.
[0018] FIG. 7A is an exemplary schematic representation of batch
etch treatment system using nozzles to dispense the steam according
to an embodiment of the present invention.
[0019] FIG. 7B depicts an exemplary schematic representation of a
single substrate etch treatment system including a treatment liquid
recycling system according to an embodiment of the present
invention.
[0020] FIGS. 8A, 8B, and 8C are exemplary schematic representations
of a transfer system for an etch treatment system in several
embodiments of the present invention.
[0021] FIG. 9 is an exemplary flowchart of a method for increasing
etch rate and etch selectivity for a masking layer of a substrate
for a batch etch treatment system using a treatment liquid and
steam in an embodiment of the present invention.
[0022] FIG. 10 is an exemplary flowchart of a method for increasing
etch rate and selectivity for a masking layer of a substrate for a
batch etch treatment system using a combined treatment liquid and
steam in an embodiment of the present invention.
[0023] FIG. 11 is an exemplary flowchart of a method for increasing
etch rate and selectivity for a masking layer of a substrate for a
batch etch treatment system using injection nozzles in an
embodiment of the present invention.
[0024] FIG. 12 is an exemplary flowchart for a method for
increasing etch rate and selectivity for a masking layer of a
substrate in a single substrate etch treatment system in an
embodiment of the present invention.
[0025] FIG. 13 is an exemplary schematic representation of a
process control system for controlling a fabrication cluster using
an etch treatment system configured to increase etch rate and etch
selectivity in an embodiment of the present invention.
[0026] FIG. 14 is an exemplary flowchart of a method for
controlling a fabrication cluster using an etch treatment system
configured to increase etch rate and etch selectivity in an
embodiment of the present invention.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENT(S)
[0027] In order to facilitate the description of the present
invention, a semiconductor substrate is utilized to illustrate an
application of the concept. The methods and processes equally apply
to other workpieces such as a wafer, disk, or the like. Similarly,
aqueous phosphoric acid is utilized to illustrate a treatment
liquid in the present invention. As mentioned below, other
treatment liquids can alternatively be used.
[0028] Referring to FIG. 1, an architectural diagram 10
illustrating prior art method of etching silicon nitride in a batch
etch treatment system where the etch chemicals (etchants) are
dispensed using one or more input streams, 34 and 38, onto the etch
processing chamber 44 where a plurality of substrates 26 are
positioned. The etchants may be reused or recycled or disposed of
using the overflow tank 42 and overflow spout 18. Heaters 22 can be
provided for example by having heaters on the sides or at the
bottom of the process chamber 44. The heaters 22 may be external or
inline.
[0029] FIG. 2 depicts an exemplary architectural diagram
illustrating a prior art batch etch treatment systems 50 for
etching silicon nitride comprising etch processing chamber 66 and
spill tank 58. As above, heaters 70 may be provided in the front,
back, and below etch processing chamber 66; these heaters 70 may be
external or inline, and may provide the heat flux in 46 into an
aqueous solution 94 in the process chamber 66. The heat flux out
comprises conduction 62 and evaporation of the water 90. If the
heat flux in is greater than the heat flux out due to evaporation
and conduction, the temperature of the aqueous solution will
increase until boiling occurs. The boiling point is fixed by the
acid concentration and atmospheric pressure. During boiling, an
increase in heat boils the water away faster. To maintain a
constant boiling temperature for the aqueous solution 94, the
process chamber controller (not shown) must regulate the heaters 70
and water supply 74 injected through supply line 78 at the same
time. If the water supply in is greater than the water loss due to
evaporation, the temperature of the aqueous solution decreases,
diluting the acid and lowering the boiling point. Conversely, if
the water supply in is less than the water loss due to evaporation,
the temperature of the aqueous solution increases, concentrating
the acid and raising the boiling point.
[0030] It is well understood that the silicon nitride etch rate in
phosphoric acid is strongly influenced by temperature, wherein the
etch rate rises in response to a rise in temperature. The chemical
reactions for etching silicon nitride and for etching silicon
dioxide are as follows:
Si.sub.3N.sub.4+4H.sub.3PO.sub.4+12H.sub.2O.fwdarw.3Si(OH).sub.4+4NH.sub-
.4H.sub.2PO.sub.4 (1)
SiO.sub.2+2H.sub.2O.fwdarw.Si(OH).sub.4 (2)
[0031] In a wet-bench configuration when immersing substrates into
a bath of aqueous phosphoric acid solution (aqueous solution), such
as in the Tokyo Electron Limited (TEL) EXPEDIUS line of tools, the
process temperature is limited by the boiling point of the aqueous
solution. The boiling point of the aqueous solution is a function
of the concentration of water in acid as well as the atmospheric
pressure, and can be described by the Clausius-Clapeyron relation
and Raoult's law. The Clausius-Clapeyron equation for the
liquid-vapor boundary can be expressed as:
ln ( P 1 P 2 ) = - .DELTA. H vap R ( 1 T 1 - 1 T 2 ) , Equation 3.0
##EQU00001##
wherein ln is natural logarithm, T.sub.1 and P.sub.1 are a
corresponding temperature (in Kelvins or other absolute temperature
units) and vapor pressure, T.sub.2 and P.sub.2 are the
corresponding temperature and pressure at another point,
.DELTA.H.sub.vap is the molar enthalpy of vaporization, and R is
the as constant (8.314 J mol.sup.-1 K.sup.-1).
[0032] Raoult's law states the vapor pressure of an ideal solution
is dependent on the vapor pressure of each chemical component and
the mole fraction of the component present in the solution. Once
the components in the solution have reached equilibrium, the total
vapor pressure p of the solution is:
p=p.sub.A*x.sub.A+p.sub.B*x.sub.B+ . . . Equation 4.0
and the individual vapor pressure for each component is
p.sub.i=p.sub.i*x.sub.i [0033] where: p.sub.i is the partial
pressure of the component i in mixture p*.sub.i is the vapor
pressure of the pure component i, and x.sub.i is the mole fraction
of the component i in solution (in mixture).
[0034] An example of equilibrium states for phosphoric acid and
water is provided in FIG. 5A. The current TEL EXPEDIUS method for
maintaining temperature is by a feedback-loop-controller that
measures the existence of a boiling state, while adjusting the
addition of water volume and heater power timing interval to the
bath so as to maintain this boiling state at a target temperature
(160 degrees C.). When the aqueous solution is heated without
addition of water the boiling point of the aqueous solution rises
as the water is evaporated from the solution.
[0035] Increasing the temperature of the phosphoric acid is
favorable for increasing the silicon nitride etch rate for
production and lower cost of manufacturing at the expense of lower
selectivity because with current phosphoric acid recirculation
tanks, the consequence of allowing a high boiling point is to
reduce the concentration of water. Water is critical in controlling
the selectivity of silicon nitride to SiO2 etching [Chemical
Reactions in Equations 1, 2]. Experimental evidence shows that a
non-boiling state (i.e., low water content) at elevated temperature
does not result in a favorable etch selectivity as shown in FIG.
5B. Conversely, to improve selectivity, it would be preferable to
have a high concentration of water (i.e., dilute the acid further);
however, this is not practical. Increasing the concentration of
water in the bath reduces the boiling point of the aqueous
solution. At lower temperature, the etch rate of the silicon
nitride falls significantly due to the strong Arrhenius
relationship of the silicon nitride etch rate with temperature.
[0036] The term treatment liquid shall be used for the rest of the
specification in order to highlight that a solvent used can be
water or some other solvent. The present invention is focused on a
novel method for increasing the delivery temperature of the
treatment liquid to the silicon nitride to increase the silicon
nitride etch rate while also maintaining high water content to
maintain optimum silicon nitride etch selectivity over silicon or
silicon dioxide. The high temperature is achieved by pressurized
steam injection into a stream of phosphoric acid before being
dispensed on a stationary or rotating single substrate.
Condensation of the steam liberates the latent heat energy into the
phosphoric acid providing an efficient transfer to heat the
phosphoric acid. An additional benefit is that the phosphoric acid
is automatically always saturated with water. Water is necessary to
maintain a high silicon nitride etch selectivity over silicon
dioxide. For a single pass process, it is necessary to have
phosphoric acid supplied with dissolved silica to assist with
selectivity control. For a recycle process, silica can be supplied
in the native phosphoric acid or by cycling of blanket silicon
nitride substrates through the etch treatment system (this is a
common process used in batch etch treatment systems, also known as
phosphoric acid baths). In an embodiment, a steam jet may also be
utilized to preheat the substrate to ensure etch uniformity from
center to edge on the substrate.
[0037] The problem solved by this invention, among others, is the
improvement of the silicon nitride etch rate process using a
treatment liquid, for example, phosphoric acid, to enable a single
substrate process to be practical and cost effective. Phosphoric
acid processing is typically seen as a "dirty process" and is
typically followed by a standard clean 1 (SC1) step to remove
particles that remain. Single substrate etch processes are
inherently cleaner than batch etch processes because the mechanism
of defect/particle redeposition and/or backside to frontside
contamination can be avoided. Silicon nitride etch processes are
slow (30-60 Angstrom/min, or A/min) in hot phosphoric acid at
16.degree. C. If the etch rate of silicon nitride can be increased
to over 180 A/min, it would make silicon nitride processing on
single substrate process tools feasible. With the use of direct
steam injection to heat the silicon nitride, high process
temperatures can be achieved while maintaining the saturated water
content required for high silicon nitride etch selectivity over
silicon or silicon dioxide.
[0038] In one embodiment, a boiling apparatus, fed liquid water at
ambient temperature, is used to generate a supply of steam water
vapor mixture at elevated pressure. The temperature of the steam
water vapor mixture can be controlled by the resulting pressure
inside the boiler. The steam water vapor mixture is then piped into
the chemical delivery line of the hot phosphoric acid to the single
substrate processing chamber. The steam water vapor mixture will
provide a source of heat and moisture to the bath, thus elevating
the bath above standard boiling temperature and introducing an
excess of water vapor in both the vapor and liquid phase to
maintain nitride etch selectivity over silicon dioxide and
silicon.
[0039] In another embodiment, the steam water vapor mixture is
combined with the treatment liquid at high pressure prior to
entering the etch processing chamber. Sufficient pressure must be
maintained to avoid boiling in the supply delivery line. The
treatment liquid will then commence rapid boiling upon entering the
etch processing chamber at ambient pressure. In another embodiment,
multiple nozzles can be used above the substrate. The first nozzle
introduces the heated phosphoric acid, the second or more nozzle(s)
introduces jets of high temperature steam water vapor mixture to
preheat the substrate surface prior to introduction of the
phosphoric acid to help with maintaining uniform temperature across
the substrate and consequently ensuring etch uniformity. In this
embodiment, the nozzle position and number of nozzles can be
positioned to maximize the efficiency of heat delivery and
treatment liquid to the substrate. The steam water vapor mixture
can also be injected onto the backside of the substrate to maintain
temperature uniformity.
[0040] FIG. 3 depicts an exemplary graph 300 of the boiling point
of phosphoric acid as a function of phosphoric acid concentration
and temperature at one atmosphere pressure. The temperature and
concentration of the treatment liquid are two key factors that
determine the etch rate and silicon nitride etch selectivity over
the silicon or silicon oxide. FIG. 3 depicts a boiling point curve
304 of the temperature of a batch etch process for silicon nitride
versus the concentration of the phosphoric acid. Referring to the
boiling point curve 304, assuming the treatment liquid is at an
initial set of conditions A, for example, the treatment liquid has
a phosphoric acid concentration of 85 percent by weight at about
120 degrees Centigrade. The treatment liquid is heated until a
boiling point is reached as represented by the point X, labeled
308, which is a point in the boiling point curve 304 that also
represents the control limit of an exemplary etch treatment system.
As mentioned above, the temperature of the treatment liquid is
increased in order to increase the etch rate while maintaining a
target silicon nitride etch selectivity and maintaining etch
uniformity at the same time.
[0041] FIG. 4A is an exemplary graph 400 comprising the boiling
point curve 404, represented on the left vertical axis, of
phosphoric acid as a function of phosphoric acid concentration at
one atmosphere pressure and a steam pressure curve 408, represented
on the right vertical axis, as a function of temperature for
mixture equilibrium conditions in an etch treatment system. The
phosphoric acid concentration is expressed as the percent weight of
phosphoric acid in the aqueous solution. Assume a set of initial
conditions of the treatment liquid at point (1) represented by a
dot, corresponding to a composition of 85% phosphoric acid by
weight and a temperature of 120 degrees Centigrade (C). The
treatment liquid is heated up and reaches boiling temperature
represented by the dotted line portion of the boiling point curve
404. Heating may utilize inline or external heaters or by injecting
steam water vapor mixture onto the etch treatment liquid. In one
embodiment, the etch treatment system has a limit high temperature
represented as point (2) on boiling point curve 404 with a
corresponding temperature of 160 degrees C. A combination of steam
and water vapor (steam water vapor mixture) is pumped into the
bottom of the etch treatment system until the treatment liquid
reaches a point (3) corresponding substantially to a composition of
92% phosphoric acid by weight, a temperature of 180 degrees C. and
a steam pressure at approximately 1.0 mega Pascals (MPa). Other
combinations of steam water vapor mixtures with aqueous phosphoric
acid can be tested to determine the etch rate and etch selectivity
of silicon nitride that meet the objectives of an application.
Pressure for the steam water vapor mixture can be in the range from
0.2 to 2.0 MPa.
[0042] Referring to FIG. 4B, assume a pressure of 0.5 MPa is
selected as the target pressure for steam water vapor mixture. The
corresponding temperature of the mixture (point A on the steam
pressure curve 408) is about 152 degrees C. As the steam water
vapor mixture is injected onto the treatment liquid in a bath or a
single substrate etch treatment system, the boiling point is
determined by the vertical line connecting point A to point A' of
the boiling point curve 404, resulting in a corresponding
phosphoric acid concentration at equilibrium of about 86%. If the
selected target pressure is 2.0 MPa, the corresponding temperature
of the mixture (point B on the steam pressure curve 408) is about
214 degrees C. Using the same approach, the boiling point is
determined by the vertical line connecting point B to point B' of
the boiling point curve 404, resulting in a corresponding
phosphoric acid concentration at equilibrium of about 96%. Thus, a
flow rate and pressure of the steam water vapor mixture can be used
as variables for controlling a temperature of the treatment liquid,
which affects the boiling point temperature of the treatment
liquid, and further resulting in a concentration of phosphoric acid
in the treatment liquid. The equilibrium phosphoric acid
concentration and temperature of the treatment liquid affects the
etch rate and etch selectivity.
[0043] FIG. 5A depicts an exemplary graph 500 comprising a first
curve 504 of the composition of phosphoric acid solutions expressed
as aqueous moles per cubic meter (Aq. mols/m3) and a second curve
508 for water expressed as mols/m3) as a function of temperature in
degrees C. As the treatment liquid is heated up in the range of 160
to 220 degrees C., the concentration of phosphoric acid is
basically flat, whereas the water concentration goes down due to
evaporation as the temperature goes up. To further illustrate the
changes to etch selectivity of the treatment liquid, FIG. 5B
depicts an exemplary graph 550 of etch selectivity of phosphoric
acid solutions as a function of time and temperature of the
treatment liquid in an etch treatment system. At the beginning of
the test, the treatment liquid, (aqueous phosphoric acid) was
boiling, and deionized water (DIW) was used to spike the treatment
liquid, etch selectivity of silicon nitride to silicon dioxide 554
was high. After 50 minutes, spiking with DIW was stopped and the
temperature of the treatment liquid crested at about 220 degrees
C., leveled at roughly the same temperature before going lower
after heater power was reduced. The etch selectivity also went down
from high to low, 554 to 558, as can be seen with the downward
slope of etch selectivity curve 564. After resuming the spiking of
the treatment liquid with DIW, the treatment liquid went into a
boiling state and the etch selectivity went from low to high, 558
to 562. The inventors found that the treatment liquid can be
advantageous at a range of 160 to 200 degrees C. and preferably
about 180 degrees C. for a treatment liquid using aqueous
phosphoric acid.
[0044] FIG. 6A depicts an exemplary schematic representation of
batch etch treatment system 600 according to an embodiment of the
present invention. A plurality of substrates 632 are positioned in
an etch processing chamber 640. A treatment liquid 628 is
introduced into the etch processing chamber 640 and excess
treatment liquid goes into an overflow container 604 and can be
disposed via a discharge spout 608. A steam generator 614 is
supplied with input liquid via delivery line 620 and is heated by
heater 616 which produces a steam water vapor mixture 612. The
steam water vapor mixture 612 is dispensed by a connection 636 onto
the bottom of the etch processing chamber 640. Using a controller
(not shown), the batch etch treatment system 600 is configured to
meet a selected etch process rate and a Fselected etch selectivity
ratio by controlling flow rates of the treatment liquid 628 and the
steam water vapor mixture 612, which may or may not be pressurized
to high pressure. Pressure for the steam water vapor mixture can be
in the range from 0.2 to 2.0 MPa.
[0045] FIG. 6B depicts an exemplary schematic representation of a
single substrate etch treatment system 650 according to an
embodiment of the present invention. A single substrate 654 is
mounted on stage 662 configured to keep the substrate 654
stationary or to rotate the substrate 654 while a treatment liquid
678 is dispensed from supply line 682 and the steam water vapor
mixture 674 is dispensed from supply delivery line 670. The steam
water vapor mixture 674 is delivered through supply delivery line
670 across the substrate 654 via nozzles 666 arranged so as to
effect uniform processing across the substrate 654. Multiple etch
treatment system setups similar to single substrate treatment
system 650 can be configured in several arrangements such as
stacked, orthogonal, or circular arrangements and the like that can
be serviced by a common substrate transfer system. Steam may be
delivered onto the backside of the substrate 654 via steam delivery
line 658 in order to preheat or maintain uniform temperature across
the substrate 654.
[0046] FIG. 7A is an exemplary schematic representation of a batch
etch treatment system 700 using nozzles 730 to dispense the steam
water vapor mixture according to an embodiment of the present
invention. A treatment liquid 738 can be heated by heaters 716
positioned in a front and back of an etch processing chamber 742.
The heaters 716 may be external or inline, providing a heat flux in
720 to the treatment liquid 738 in the etch processing chamber 742.
Furthermore, an additional heat flux in 722 is provided by the
injection of steam water vapor mixture 736 in the treatment liquid
738, delivered via supply delivery line 726. The heat flux out
comprises conduction 708 and evaporation of the water 734. If the
heat flux in is greater than the heat flux out 708, 734 due to
evaporation and conduction, a temperature of the treatment liquid
738 will increase until boiling occurs. The boiling point is fixed
by the treatment liquid 738 concentration and atmospheric pressure.
During boiling, an increase in heat boils the water away
faster.
[0047] To maintain a constant boiling temperature for the treatment
liquid 738, the process chamber controller (not shown) must
regulate the heaters 716 and the injection of steam water vapor
mixture through nozzles 730 at the same time. If the supply of
steam water vapor mixture is greater than the water loss due to
evaporation, the temperature of the treatment liquid 738 decreases,
diluting the treatment liquid 738 and lowering the boiling point.
Conversely, if the water supply in is less than the water loss due
to evaporation, the temperature of the treatment liquid 738
increases, concentrating the acid and raising the boiling point.
Placing the nozzles 730 at a bottom of the etch processing chamber
742 provides mixing actions so as to create a uniform temperature
profile in the treatment liquid 738. The treatment liquid 738 can
be introduced via the second supply delivery line 724 to the
nozzles 730. Excess treatment liquid 738 goes to a spill tank 704.
The batch etch treatment system 700 provides a way to increase the
etch rate of a masking layer, for example, silicon nitride by
raising a temperature of the treatment liquid 738. The target etch
selectivity, the ratio of silicon nitride etching over the silicon
oxide or silicon, is also maintained by controlling the molarity of
the treatment liquid 738, for example, by adding more or less steam
water vapor mixture, and/or increasing or decreasing the
temperature of the steam water vapor mixture distributed through
the nozzles 730.
[0048] FIG. 7B depicts an exemplary schematic representation of a
single substrate etch treatment system 760 including a treatment
liquid recycling system 783 according to an embodiment of the
present invention. Recycling the treatment liquid 774 reduces
chemical usage and assist etch selectivity by keeping a high
concentration of silica in the treatment liquid to keep the
equilibrium of Reaction 2 to the left as will be discussed further
below. Referring to the single substrate etch treatment system 760,
a single substrate 796 is positioned on a stage 788 configured to
make the substrate 796 stationary or rotating inside the etch
processing chamber 762. A steam water vapor mixture 766 is
delivered using supply line 764 and dispensed onto the substrate
using nozzles 790. Steam 769 is dispensed using a steam input line
768 onto the back surface of the substrate 796 to maintain a
uniform temperature for the substrate 796. The steam 769 may be the
same as the steam water vapor mixture 766. The treatment liquid
recycling system 783 comprises a drain line 786 coupled to the
bottom of the etch processing chamber 762 and goes through a
control valve 782 that disposes a portion of the treatment liquid
774 through disposal line 780 and recycles the balance of the
treatment liquid 774 through recycle line 784. An optional heater
778 may be positioned before or after the liquid treatment delivery
line 776 to maintain a desired temperature of the recycled
treatment liquid 774. New treatment liquid 774 is introduced onto
the recycle line 784 using treatment liquid delivery line 776.
[0049] Referring to FIG. 7B, dissolved silica assists in
maintaining the target silicon nitride etch rate by inhibiting
Reaction 2. In one embodiment, dissolved silica (Si(OH).sub.4) is
injected onto the treatment liquid 774 using a silica injection
line 772 and using delivery line 776, the amount of silica
sufficient to maintain the amount of dissolved silica at a certain
target range, for example, 10 to 30 ppm dissolved silica. In one
implementation, the dissolved silica can be 20 ppm. In another
embodiment, a number of substrates 796 containing silicon nitride
is processed in order to obtain a desired amount of dissolved
silica in the recycled treatment liquid 774. One advantage of the
present invention using a single substrate treatment system is
tolerance for a higher concentration of silica in the treatment
liquid. Prior art batch etch treatment systems using phosphoric
acid typically shows an increase in defect rate as the
concentration of silica went up. A single substrate treatment
system is inherently advantageous due to lower defect rate than
batch etch treatment systems for the same application, in addition
to tolerance of the higher concentration of silica which helps
maintain a stable selectivity ratio of the masking layer to the
silicon oxide.
[0050] FIGS. 8A, 8B, and 8C are exemplary schematic representations
of a transfer system for an etch treatment system in several
embodiments of the present invention. According to one embodiment,
FIG. 8A depicts a processing system 800 for performing a non-plasma
cleaning process on a substrate or on substrates. The processing
system 800 comprises a first treatment system 816, and a second
treatment system 812 coupled to the first treatment system 816. For
example, the first treatment system 816 can comprise a chemical
treatment system (or chemical treatment component of a single
process chamber), and the second treatment system 812 can comprise
a thermal treatment system (or thermal treatment component of a
single process chamber).
[0051] Also, as illustrated in FIG. 8A, a transfer system 808 can
be coupled to the first treatment system 816 in order to transfer a
substrate or substrates into and out of the first treatment system
816 and the second treatment system 812, and exchange substrates
with a multi-element manufacturing system 804. The first and second
treatment systems 816, 812, and the transfer system 808 can, for
example, comprise a processing element within the multi-element
manufacturing system 804. For example, the multi-element
manufacturing system 804 can permit the transfer of a substrate or
substrates to and from processing elements including such devices
as etch treatment systems, deposition system, coating systems,
patterning systems, metrology systems, etc. In order to isolate the
processes occurring in the first and second systems, an isolation
assembly 820 can be utilized to couple each system. For instance,
the isolation assembly 820 can comprise at least one of a thermal
insulation assembly to provide thermal isolation, and a gate valve
assembly to provide vacuum isolation. Of course, treatment systems
816 and 812, and transfer system 808 can be placed in any
sequence.
[0052] Alternately, in another embodiment, FIG. 8B presents a
processing system 850 for performing a non-plasma cleaning process
on a substrate. The processing system 850 comprises a first
treatment system 856, and a second treatment system 858. For
example, the first treatment system 856 can comprise a chemical
treatment system, and the second treatment system 858 can comprise
a thermal treatment system.
[0053] Also, as illustrated in FIG. 8B, a transfer system 854 can
be coupled to the first treatment system 856 in order to transfer a
substrate or substrates into and out of the first treatment system
856, and can be coupled to the second treatment system 858 in order
to transfer a substrate or substrates into and out of the second
treatment system 858. Additionally, transfer system 854 can
exchange a substrate or substrates with one or more substrate
cassettes (not shown). Although only two process systems are
illustrated in FIG. 8B, other process systems can access transfer
system 854 including such devices as etch treatment systems,
deposition systems, coating systems, patterning systems, metrology
systems, etc. In order to isolate the processes occurring in the
first and second systems, an isolation assembly 862 can be utilized
to couple each system. For instance, the isolation assembly 862 can
comprise at least one of a thermal insulation assembly to provide
thermal isolation, and a gate valve assembly to provide vacuum
isolation. Additionally, for example, the transfer system 854 can
serve as part of the isolation assembly 862.
[0054] Alternately, in another embodiment, FIG. 8C presents a
processing system 870 for performing a non-plasma cleaning process
on a substrate or on substrates. The processing system 870
comprises a first treatment system 886, and a second treatment
system 882, wherein the first treatment system 886 is stacked atop
the second treatment system 882 in a vertical direction as shown.
For example, the first treatment system 886 can comprise a chemical
treatment system, and the second treatment system 882 can comprise
a thermal treatment system.
[0055] Also, as illustrated in FIG. 8C, a transfer system 878 can
be coupled to the first treatment system 886 in order to transfer a
substrate or substrates into and out of the first treatment system
886, and can be coupled to the second treatment system 882 in order
to transfer a substrate or substrates into and out of the second
treatment system 882. Additionally, transfer system 878 can
exchange a substrate or substrates with one or more substrate
cassettes (not shown). Although only two process systems are
illustrated in FIG. 8C, other process systems can access transfer
system 878 including such devices as etch treatment systems,
deposition systems, coating systems, patterning systems, metrology
systems, etc. In order to isolate the processes occurring in the
first and second systems, an isolation assembly 874 can be utilized
to couple each system. For instance, the isolation assembly 874 can
comprise at least one of a thermal insulation assembly to provide
thermal isolation, and a gate valve assembly to provide vacuum
isolation. Additionally, for example, the transfer system 878 can
serve as part of the isolation assembly 874. As illustrated above,
the chemical treatment system and the thermal treatment system may
comprise separate process chambers coupled to one another.
Alternatively, the chemical treatment system and the thermal
treatment system may be a component of a single process
chamber.
[0056] FIG. 9 is an exemplary flowchart for a method 900 for
increasing etch rate and etch selectivity for a masking layer of a
substrate for a batch etch treatment system using a treatment
liquid and steam water vapor mixture in an embodiment. In step 904,
a target etch rate and target etch selectivity ratio for the
masking layer over silicon oxide or silicon are selected. The
masking layer can be silicon nitride, gallium nitride or aluminum
nitride and the like. In step 908, a supply of steam water vapor
mixture at an elevated pressure is obtained. The steam water vapor
mixture may be provided by an inline steam generator or from a
general purpose steam source in the fabrication cluster. In step
912, a supply of a treatment liquid for selectively etching a
masking layer is obtained. The treatment liquid can include
phosphoric acid, hydrofluoric acid, or hydrofluoric acid/ethylene
glycol and the like. In step 916, a plurality of substrates is
placed in the etch processing chamber. In step 920, the treatment
liquid is dispensed in the etch processing chamber, wherein
dispensing can be performed using a supply delivery line or a using
nozzle. In step 924, a flow of steam water vapor mixture is
injected into the etch processing chamber, wherein the flow rate of
the steam water vapor mixture is controlled to achieve the target
etch rate for the masking layer and target etch selectivity of the
masking layer over the silicon oxide or silicon. The flow rate of
the steam water vapor mixture can be correlated to data based on
treatment liquid concentration, temperature of the aqueous
solution, and steam pressure as shown in FIGS. 4A and 4B. As
mentioned in the description of FIG. 4B, a flow rate and pressure
of the steam water vapor mixture can be used as variables for
controlling a temperature of the treatment liquid, which affects
the boiling point temperature of the treatment liquid and further
resulting in a concentration of phosphoric acid in the treatment
liquid. The equilibrium phosphoric acid concentration and
temperature affects the etch rate and etch selectivity.
[0057] FIG. 10 is an exemplary flowchart for a method 1000 for
increasing etch rate and etch selectivity for a masking layer of a
substrate in a batch etch treatment system using a combined
treatment liquid and steam water vapor mixture. In step 1004, a
target etch rate and target etch selectivity for the masking layer
over silicon oxide or silicon are selected. The masking layer can
be silicon nitride, gallium nitride, or aluminum nitride and the
like. In step 1008, a supply of steam water vapor mixture at an
elevated pressure is obtained. The supply may be provided by an
inline steam generator or from a general purpose steam source in
the fabrication cluster. In step 1012, a supply of a treatment
liquid for selectively etching a masking layer is obtained. The
treatment liquid can include phosphoric acid, hydrofluoric acid, or
hydrofluoric acid/ethylene glycol and the like. In step 1016, a
plurality of substrates is placed in the etch processing chamber.
In step 1020, the treatment liquid is combined with the steam water
vapor mixture in a mixing tank or in a supply delivery line.
Sufficient pressure must be maintained to avoid boiling in the
supply delivery line. The treatment liquid will commence rapid
boiling upon entering the etch processing chamber at ambient
pressure.
[0058] Referring to FIG. 10, in step 1024, a flow of the combined
steam water vapor mixture and treatment liquid is injected into the
etch processing chamber, wherein the flow rate of the steam water
vapor mixture is controlled to achieve the target etch rate for the
masking layer and target etch selectivity of the masking layer over
the silicon oxide or silicon. As mentioned above, the flow rate of
the steam water vapor mixture can be correlated to data based on
treatment liquid concentration, temperature of the aqueous
solution, and steam pressure as shown in FIGS. 4A and 4B. As
mentioned in the description of FIG. 4B, a flow rate and pressure
of the steam water vapor mixture can be used as variables for
controlling a temperature of the treatment liquid, which affects
the boiling point temperature of the treatment liquid and further
resulting in a concentration of phosphoric acid in the treatment
liquid. The equilibrium phosphoric acid concentration and
temperature affects the etch rate and etch selectivity.
[0059] The correlation can be used to determine the flow rate
needed to meet the target etch rate and target etch selectivity. In
one embodiment, the steam water vapor mixture and treatment liquid
are combined in a supply delivery line before entering the etch
processing chamber. In another embodiment, the steam water vapor
mixture and treatment liquid are combined immediately before
exiting the supply delivery line in the etch processing
chamber.
[0060] FIG. 11 is an exemplary flowchart for a method 1100 for
increasing etch rate and etch selectivity for a masking layer of a
substrate in a batch etch treatment system using a plurality of
nozzles positioned at a bottom and sides of the etch processing
chamber. In step 1104, a target etch rate and target etch
selectivity for the masking layer over silicon oxide or silicon are
selected. The masking layer can be silicon nitride, gallium
nitride, or aluminum nitride and the like. In step 1108, a supply
of steam water vapor mixture at an elevated pressure is obtained.
The supply may be provided by an inline steam generator or from a
general purpose steam source in the fabrication cluster. In step
1112, a supply of a treatment liquid for selectively etching a
masking layer is obtained. The treatment liquid can include
phosphoric acid, hydrofluoric acid, or hydrofluoric acid/ethylene
glycol and the like. In step 1116, a plurality of substrates is
placed in the etch processing chamber. In step 1120, the treatment
liquid is dispensed in the etch processing chamber.
[0061] In step 1124, a flow of the combined steam water vapor
mixture and treatment liquid is injected into the etch processing
chamber using the plurality of nozzles, wherein the flow rate of
the steam water vapor mixture is controlled to achieve the target
etch rate for the masking layer and target etch selectivity of the
masking layer over the silicon oxide or silicon. The plurality of
nozzles can be positioned in the bottom and/or on the sides of the
etch processing chamber. Arrangements of the plurality of nozzles
can be varied to ensure temperature uniformity and consequently
etching uniformity. As mentioned above, the flow rate of the steam
water vapor mixture can be correlated to data based on treatment
liquid concentration, temperature of the aqueous solution, and
steam pressure as shown in FIGS. 4A and 4B. As mentioned in the
description of FIG. 4B, a flow rate and pressure of the steam water
vapor mixture can be used as variables for controlling a
temperature of the treatment liquid, which affects the boiling
point temperature of the treatment liquid and further resulting in
a concentration of phosphoric acid in the treatment liquid. The
equilibrium phosphoric acid concentration and temperature affects
the etch rate and etch selectivity.
[0062] FIG. 12 is an exemplary flowchart for a method for
increasing etch rate and etch selectivity for a layer of a
substrate in a single substrate etch treatment system. In step
1204, a target etch rate and target etch selectivity for the
masking layer over silicon oxide or silicon, and/or target
completion time are selected. The masking layer can be silicon
nitride, gallium nitride, or aluminum nitride and the like. In step
1208, a supply of steam water vapor mixture at an elevated pressure
is obtained. The supply may be provided by an inline steam
generator or from a general purpose steam source in the fabrication
cluster. In step 1212, a supply of a treatment liquid for
selectively etching a masking layer is obtained. The treatment
liquid can include phosphoric acid, hydrofluoric acid, or
hydrofluoric acid/ethylene glycol and the like. In step 1216, a
single substrate is placed in the etch processing chamber. In one
embodiment, two or more etch processing chambers can be configured
such that these chambers can be supplied with the treatment liquid,
supplied with steam water vapor mixture, and loaded with and
unloaded of substrates. In step 1220, the treatment liquid is
dispensed in the etch processing chamber, wherein dispensing can be
performed using a supply delivery line or a nozzle. In step 1224, a
flow of steam water vapor mixture and/or treatment liquid is
injected into the etch processing chamber using one or more nozzles
while the substrate is spinning. Alternatively, the substrate can
be stationary while the nozzles are made to rotate.
[0063] Referring to FIG. 12, in one embodiment, the treatment
liquid and steam water vapor mixture are combined in the supply
delivery line prior to entry into the etch processing chamber or
after entry into the etch processing chamber but prior to exit out
of the nozzle. Sufficient pressure must be maintained in order to
avoid boiling in the supply delivery line. The treatment liquid
will then commence rapid boiling upon entering the processing
chamber at ambient pressure. In another embodiment, multiple
nozzles can be used above the substrate. The first nozzle
introduces the heated phosphoric acid, the second or more nozzle(s)
introduce jets of high temperature steam to preheat the substrate
surface prior to introduction of the phosphoric acid to help
maintain uniform temperature across the substrate and ensure etch
uniformity. In another embodiment, the nozzle position and number
of nozzles can be positioned to maximize the efficiency of heat
delivery and treatment liquid to the substrate. In still another
embodiment, steam water vapor mixture can also be injected onto the
backside of the substrate to maintain temperature uniformity.
[0064] FIG. 13 is an exemplary block diagram of a system 1300 for
determining and utilizing profile parameters of a structure on a
substrate after etch processing where the profile parameter values
are used for automated process and equipment control. System 1300
includes a first fabrication cluster 1302 and optical metrology
system 1304. System 1300 also includes a second fabrication cluster
1306. For details of an optical metrology system used to determine
profile parameters of a structure on a substrate, refer to U.S.
Pat. No. 6,943,900, titled GENERATION OF A LIBRARY OF PERIODIC
GRATING DIFFRACTION SIGNALS, issued on Sep. 13, 2005, which is
incorporated herein by reference in its entirety. Although the
second fabrication cluster 1306 is depicted in FIG. 13 as being
subsequent to first fabrication cluster 1302, it should be
recognized that second fabrication cluster 1306 can be located
prior to first fabrication cluster 1302 in system 1300, for
example, in the manufacturing process flow.
[0065] A photolithographic process, such as exposing and/or
developing a photoresist layer applied to a substrate, can be
performed using first fabrication cluster 1302. In one exemplary
embodiment, optical metrology system 1304 includes an optical
metrology tool 1308 and processor 1310. Optical metrology tool 1308
is configured to measure a diffraction signal off the sample
structure. Processor 1310 is configured to use the measured
diffraction signal measured by the optical metrology tool and
adjust using a signal adjuster, generating an adjusted metrology
output signal. Furthermore, processor 1310 is configured to compare
the adjusted metrology output signal to the simulated diffraction
signal. As mentioned above, the simulated diffraction is determined
using an optical metrology tool model using ray tracing, a set of
profile parameters of the structure and numerical analysis based on
the Maxwell equations of electromagnetic diffraction. In one
exemplary embodiment, optical metrology system 1304 can also
include a library 1312 with a plurality of simulated diffraction
signals and a plurality of values of one or more profile parameters
associated with the plurality of simulated diffraction signals. As
described above, the library can be generated in advance; metrology
processor 1310 can compare an adjusted metrology output signal to
the plurality of simulated diffraction signals in the library. When
a matching simulated diffraction signal is found, the one or more
values of the profile parameters associated with the matching
simulated diffraction signal in the library is assumed to be the
one or more values of the profile parameters used in the substrate
application to fabricate the sample structure.
[0066] System 1300 also includes a metrology processor 1316. In one
exemplary embodiment, processor 1310 can transmit the one or more
values of the one or more profile parameters to metrology processor
1316. Metrology processor 1316 can then adjust one or more process
parameters or equipment settings of the first fabrication cluster
1302 based on the one or more values of the one or more profile
parameters determined using optical metrology system 1304.
Metrology processor 1316 can also adjust one or more process
parameters or equipment settings of the second fabrication cluster
1306 based on the one or more values of the one or more profile
parameters determined using optical metrology system 1304. As noted
above, second fabrication cluster 1306 can process the substrate
before or after fabrication cluster 1302. In another exemplary
embodiment, processor 1310 is configured to train machine learning
system 1314 using the set of measured diffraction signals as inputs
to machine learning system 1314 and profile parameters as the
expected outputs of machine learning system 1314.
[0067] FIG. 14 is an exemplary flowchart of a method for
controlling a fabrication cluster using an etch treatment system
configured to increase etch rate and etch selectivity. Using the
system described in FIG. 13, after etch processing using the
systems and methods described in relation to FIGS. 3 to 12, the
structure in the substrate can be measured using the method as
depicted with the exemplary block diagram 1400 of a system for
determining and utilizing profile parameters for automated process
and equipment control. In step 1410, a measured diffraction signal
off a sample structure is obtained using an optical metrology tool.
In step 1420, a metrology output signal is determined from the
measured diffraction signal using ray tracing methodology,
calibration parameters of the optical metrology device, and one or
more accuracy criteria or other scatterometry methodologies such as
regression, library matching or machine learning systems. In step
1430, at least one profile parameter of the sample structure is
determined using the metrology output signal. In step 1440, at
least one fabrication process parameter or an equipment setting is
modified using at least one profile parameter of the structure.
[0068] Referring to FIGS. 6A and 6B, a controller (not shown) can
be used to control the flow rates of the treatment liquid and steam
water vapor mixture, pressure of the treatment liquid, sequencing
of the use of the nozzles in the batch or single substrate etch
application. A program stored in the memory of the controller can
be utilized to activate the inputs to the aforementioned components
of the etch treatment systems 600 650 (FIGS. 6A and 6B) according
to a process recipe in order to perform the method of increasing
the etch rate and etch selectivity of the masking layer compared to
silicon or silicon oxide. One example of controller 1090 is a DELL
PRECISION WORKSTATION 610.sup.TH, available from Dell Corporation,
Austin, Tex. A controller can be locally located relative to the
etch treatment systems 600 650, or it can be remotely located
relative to the etch treatment systems 600 650, via an internet or
intranet. Thus, the controller can exchange data with the etch
treatment systems 600 650, using at least one of a direct
connection, an intranet, or the internet. The controller can be
coupled to an intranet at a customer site (i.e., a device maker,
etc.), or coupled to an intranet at a vendor site (i.e., an
equipment manufacturer). Furthermore, another computer (i.e.,
controller, server, etc.) can access the controller of the etch
treatment systems 600 650 to exchange data via at least one of a
direct connection, an intranet, or the internet.
[0069] Although exemplary embodiments have been described, various
modifications can be made without departing from the spirit and/or
scope of the present invention. For example, the invention was
illustrated and described utilizing etching of a masking layer on a
substrate, specifically, silicon nitride. Other masking materials
or insulating layers can be processed using the same methods and
systems described in the specification. Therefore, the present
invention should not be construed as being limited to the specific
forms shown in the drawings and described above. Accordingly, all
such modifications are intended to be included within the scope of
this invention.
* * * * *