U.S. patent application number 13/632770 was filed with the patent office on 2013-01-31 for processing condition inspection and optimization method of damage recovery process, damage recovering system and storage medium.
The applicant listed for this patent is Reiko SASAHARA, Shigeru Tahara, Jun Tamura. Invention is credited to Reiko SASAHARA, Shigeru Tahara, Jun Tamura.
Application Number | 20130025537 13/632770 |
Document ID | / |
Family ID | 40720685 |
Filed Date | 2013-01-31 |
United States Patent
Application |
20130025537 |
Kind Code |
A1 |
SASAHARA; Reiko ; et
al. |
January 31, 2013 |
PROCESSING CONDITION INSPECTION AND OPTIMIZATION METHOD OF DAMAGE
RECOVERY PROCESS, DAMAGE RECOVERING SYSTEM AND STORAGE MEDIUM
Abstract
A processing condition inspection method of a damage recovery
process for reforming a film having OH groups generated by damages
from a predetermined process by using a processing gas includes
preparing a substrate having an OH group containing resin film,
measuring an initial film thickness of the OH group containing
resin film, performing a damage recovery process on the substrate
after measuring the initial film thickness, measuring a film
thickness of the OH group containing resin film after the damage
recovery process, calculating a film thickness difference of the OH
group containing resin film before and after the damage recovery
process, and determining whether processing conditions of the
damage recovery process are appropriate or inappropriate based on
the film thickness difference.
Inventors: |
SASAHARA; Reiko;
(Nirasaki-shi, JP) ; Tamura; Jun; (Nirasaki-shi,
JP) ; Tahara; Shigeru; (Nirashaki-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SASAHARA; Reiko
Tamura; Jun
Tahara; Shigeru |
Nirasaki-shi
Nirasaki-shi
Nirashaki-shi |
|
JP
JP
JP |
|
|
Family ID: |
40720685 |
Appl. No.: |
13/632770 |
Filed: |
October 1, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12326507 |
Dec 2, 2008 |
8282984 |
|
|
13632770 |
|
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|
61082054 |
Jul 18, 2008 |
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61034510 |
Mar 7, 2008 |
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Current U.S.
Class: |
118/697 |
Current CPC
Class: |
H01L 22/12 20130101 |
Class at
Publication: |
118/697 |
International
Class: |
C23C 16/52 20060101
C23C016/52 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 3, 2007 |
JP |
2007-312562 |
Jun 5, 2008 |
JP |
2008-147701 |
Claims
1. A damage recovering system comprising: a silylation processing
apparatus configured to reform a film containing OH group generated
by damages from an etching or an ashing process by a silylation
process; a film thickness measurement device configured to measure
a film thickness of the film; a transfer device configured to
transfer a substrate having the film to the film thickness
measurement device; and a control unit which includes: a controller
having a micro processer; a storage unit storing control programs;
and a user interface by which one of the control programs is
retrieved from the storage unit and executed in the controller,
wherein the control unit is configured to control the damage
recovering system to perform: (a) determining an optimization
condition of the silylation process; (b) transferring the substrate
into the silylation processing apparatus; (c) setting the
silylation processing apparatus to the optimization condition of
the silylation process, and (d) performing the silylation process
on the film by the silylation processing apparatus, wherein said
determining the optimization condition of the silylation process
includes: (a-1) preparing a substrate having a resist film
containing OH group; (a-2) measuring an initial film thickness of
the resist film; (a-3) performing a damage recovery process on the
resist film by using a processing gas containing a silylation agent
after measuring the initial film thickness, wherein a film
thickness of the resist film is increased after performing the
damage recovery process; (a-4) measuring a film thickness of the
resist after the damage recovery process; (a-5) calculating a film
thickness difference of the resist before and after the damage
recovery process; and (a-6) adjusting a processing condition of the
damage recovery process performed by using the processing gas
containing the silylation agent such that the film thickness
difference of the resist film before and after the damage recovery
process has a value corresponding to an optimal processing
condition based on previously obtained data for a relationship
between the thickness difference and the processing condition of
damage recovery process performed by using the processing gas
containing the silylation agent, and wherein said adjusting
includes adjusting the processing condition such that an amount of
increased film thickness of the resist film after the damage
recovery process is within a tolerance range.
2. The damage recovering system of claim 1, wherein the film
containing OH group generated by the damages is a low-k interlayer
dielectric film.
3. The damage recovering system of claim 1, wherein the resist film
is a KrF resist film.
4. The damage recovering system of claim 1, wherein the film
thickness of the resist film after the damage recovery process is
larger than the initial film thickness due to reaction of the
processing gas.
5. The damage recovering system of claim 1, wherein the damage
recovery process performed on the resist film is carried out at a
temperature of 120 to 350.degree. C.
6. The damage recovering system of claim 1, wherein the damage
recovery process performed on the resist film is carried out at a
pressure of 1 to 50 Torr (133 to 6666 Pa).
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a divisional application of pending U.S.
application Ser. No. 12/326,507, filed Dec. 2, 2008, the entire
contents of which is incorporated herein by reference. U.S.
application Ser. No. 12/326,507 claims the benefit of priority
under 119(e) of U.S. Provisional Application No. 61/082,054, filed
on Jul. 18, 2008 and U.S. Provisional Application No. 61/034,510,
filed on Mar. 7, 2008, and also claims the benefit of priority to
Japanese Patent Application No. 2007-312562, filed on Dec. 3, 2007
and Japanese Patent Application No. 2008-147701, filed on Jun. 5,
2008.
FIELD OF THE INVENTION
[0002] The present invention relates to a processing condition
inspection method and a processing condition optimization method of
a damage recovery process for a film, e.g., a low dielectric film
serving as an interlayer insulating film formed by a damascene
method in a semiconductor device, having OH groups generated by
etching damages or ashing damages, a damage recovering system and a
storage medium.
BACKGROUND OF THE INVENTION
[0003] In a semiconductor device manufacturing process, a dual
damascene method is widely used to form a wiring groove or a
contact hole (see, e.g., Patent Document 1).
[0004] Meanwhile, as semiconductor devices are miniaturized, a
parasitic capacitance of an interlayer insulating film has become
an important factor to improve wiring performance. The interlayer
insulating film employs a low dielectric constant film (low-k film)
made of a low-k material. Further, the low-k film is generally made
of a material having end groups of alkyl groups such as methyl
groups.
[0005] However, in the aforementioned conventional damascene
process, the low-k film is damaged during an etching process or a
resist film removing process (ashing process). This damage
increases the dielectric constant of the low-k film, and decreases
effects obtained by using the low-k film as the interlayer
insulating film.
[0006] As a technique for recovering such damage, Patent Document 2
discloses a method for performing a silylation process after
etching or removal of the resist film. The silylation process is
performed to reform a damaged surface portion having end groups of
OH groups by using a silylation agent such that the OH end groups
can be replaced by alkyl groups such as methyl groups.
[0007] In order to apply the damage recovery process to a mass
production system, it is required to check whether the apparatus is
normal or not by inspecting processing conditions in a chamber
set-up of the silylation processing apparatus or a daily check.
Currently, in order to inspect the processing conditions, etching
and ashing processes are performed on a wafer having a low-k film
and a silylation process is performed thereon to prepare a sample.
Then, a dilute hydrofluoric acid treatment is performed on the
sample, wherein CDs or film thicknesses t are measured before and
after the dilute hydrofluoric acid treatment to obtain .DELTA.CD or
.DELTA.t, thereby inspecting the processing conditions.
[0008] However, when the processing conditions are inspected by the
above-described technique, the sample needs to be prepared by
performing etching and ashing before the silylation process.
Therefore, the sample preparation time is required and, also, the
processing conditions related only to the silylation processing
apparatus cannot be inspected. In other words, even if .DELTA.CD or
.DELTA.t is abnormal, it is not possible to determine whether the
problem is related to the silylation process or to etching/ashing
process.
[0009] Further, even if silylation conditions such as a gas
concentration vary, .DELTA.CD or .DELTA.t obtained after the dilute
hydrofluoric acid treatment is hardly changed. Furthermore, even if
the same .DELTA.CD or .DELTA.t is obtained after the dilute
hydrofluoric acid treatment on different samples, these samples
often reveal different electrical characteristics. Namely, the
processing conditions of the silylation process can not verified
reliably.
[0010] [Patent Document 1] Japanese Patent Laid-open Publication
No. 2002-083869
[0011] [Patent Document 2] Japanese Patent Laid-open Publication
No. 2006-049798
SUMMARY OF THE INVENTION
[0012] In view of the above, the present invention provides a
processing condition inspection method and a processing condition
optimization method of a damage recovery process, capable of
inspecting processing conditions only by a damage recovery process
and precisely detecting abnormality of the processing conditions,
and a processing condition optimization method.
[0013] Further, the present invention provides a damage recovering
system capable of executing the above methods and a storage medium
storing a program for implementing the above methods.
[0014] In accordance with a first aspect of the present invention,
there is provided a processing condition inspection method of a
damage recovery process for reforming a film having OH groups
generated by damages from a predetermined process by using a
processing gas, comprising: preparing a substrate having an OH
group containing resin film; measuring an initial film thickness of
the OH group containing resin film; performing a damage recovery
process on the substrate after measuring the initial film
thickness; measuring a film thickness of the OH group containing
resin film after the damage recovery process; calculating a film
thickness difference of the OH group containing resin film before
and after the damage recovery process; and determining whether
processing conditions of the damage recovery process are
appropriate or inappropriate based on the film thickness
difference.
[0015] In accordance with a second aspect of the present invention,
there is provided a processing condition optimization method of a
damage recovery process for reforming a film having OH groups
generated by damages from a predetermined process by using a
processing gas, comprising: preparing a substrate having an OH
group containing resin film; measuring an initial film thickness of
the OH group containing resin film; performing a damage recovery
process on the substrate after measuring the initial film
thickness; measuring a film thickness of the OH group containing
resin film after the damage recovery process; calculating a film
thickness difference of the OH group containing resin film before
and after the damage recovery process; and adjusting processing
conditions such that the film thickness difference of the OH group
containing resin film before and after the damage recovery process
has a value corresponding to optimal processing conditions based on
previously obtained data for a relationship between the processing
conditions and the film thickness difference.
[0016] In the first and second aspects, the film having the OH
groups generated by the damages may be a low-k interlayer
insulating film. Further, the OH group containing resin film may be
an OH group containing photoresist film. In this case, preferably,
the OH group containing photoresist film is a KrF resist film.
Further, the film thickness of the OH group containing resin film
after the damage recovery process may be larger than the initial
film thickness due to reaction of the processing gas. Further, the
damage recovery process may be performed by a silylation process
using a silylation agent as a processing gas. Further, the
predetermined process causing the damages may be etching and/or
ashing.
[0017] In the second aspect, when the damage recovery process is
performed by a silylation process using a silylation agent as a
processing gas, preferably, the silylation process is performed at
a temperature of 120 to 350.degree. C. Further, preferably, the
silylation process is performed at a processing gas pressure of 1
to 50 Torr (133 to 6666 Pa).
[0018] In accordance with a third aspect of the present invention,
there is provided a damage recovering system comprising: a damage
recovering apparatus for reforming a film having OH groups
generated by damages from a predetermined process by using a
processing gas; a film thickness measurement device for measuring a
film thickness of a predetermined film; and a control unit for
controlling operations of the system, the operations including
loading a substrate having an OH group containing resin film into
the film thickness measurement device, measuring an initial film
thickness of the OH group containing resin film, performing a
damage recovery process on the substrate in the damage recovering
apparatus after measuring the initial film thickness, measuring a
film thickness of the OH group containing resin film in the film
thickness measurement device after the damage recovery process,
calculating a film thickness difference of the OH group containing
resin film before and after the damage recovery process, and
determining whether processing conditions of the damage recovery
process are appropriate or inappropriate based on the film
thickness difference.
[0019] In accordance with a fourth aspect of the present invention,
there is provided a damage recovering system comprising: a damage
recovering apparatus for reforming a film having OH groups
generated by damages from a predetermined process by using a
processing gas; a film thickness measurement device for measuring a
film thickness of a predetermined film; and a control unit for
controlling operations of the system, the operations including
loading a substrate having an OH group containing resin film into
the film thickness measurement device, measuring an initial film
thickness of the OH group containing resin film, performing a
damage recovery process on the substrate in the damage recovering
apparatus after measuring the initial film thickness, measuring a
film thickness of the OH group containing resin film in the film
thickness measurement device after the damage recovery process,
calculating a film thickness difference of the OH group containing
resin film before and after the damage recovery process, and
adjusting processing conditions such that the film thickness
difference of the OH group containing resin film before and after
the damage recovery process has a value corresponding to optimal
processing conditions based on previously obtained data for a
relationship between the processing conditions and the film
thickness difference.
[0020] In accordance with a fifth aspect of the present invention,
there is provided a computer-readable storage medium storing a
program for controlling a damage recovering system including a
damage recovering apparatus for reforming a film having OH groups
generated by damages from a predetermined process by using a
processing gas and a film thickness measurement device for
measuring a film thickness of a predetermined film, wherein the
program, when executed, controls the damage recovering system to
perform a processing condition inspection method of a damage
recovery process, the method including: preparing a substrate
having an OH group containing resin film; measuring an initial film
thickness of the OH group containing resin film; performing a
damage recovery process on the substrate after measuring the
initial film thickness; measuring a film thickness of the OH group
containing resin film after the damage recovery process;
calculating a film thickness difference of the OH group containing
resin film before and after the damage recovery process; and
determining whether processing conditions of the damage recovery
process are appropriate or inappropriate based on the film
thickness difference.
[0021] In accordance with a sixth aspect of the present invention,
there is provided a computer-readable storage medium storing a
program for controlling a damage recovering system including a
damage recovering apparatus for reforming a film having OH groups
generated by damages from a predetermined process by using a
processing gas and a film thickness measurement device for
measuring a film thickness of a predetermined film, wherein the
program, when executed, controls the damage recovering system to
perform a processing condition inspection method of a damage
recovery process, the method including: preparing a substrate
having an OH group containing resin film; measuring an initial film
thickness of the OH group containing resin film; performing a
damage recovery process on the substrate after measuring the
initial film thickness; measuring a film thickness of the OH group
containing resin film after the damage recovery process;
calculating a film thickness difference of the OH group containing
resin film before and after the damage recovery process; and
adjusting processing conditions such that the film thickness
difference of the OH group containing resin film before and after
the damage recovery process has a value corresponding to optimal
processing conditions based on previously obtained data for a
relationship between the processing conditions and the film
thickness difference. The present inventors carried out repeated
examination based on the fact that the damages inflicted on the
low-k film by etching or ashing cause generation of OH groups, and
a damage recovery process, for example, a silylation process, is
performed to reform a portion having the OH groups. As a result,
they have found that the processing conditions can be inspected
simply and precisely by performing the damage recovery process on a
substrate having an OH group containing resin film and calculating
a film thickness difference of the OH group containing resin film
before and after the damage recovery process before a damage
recovery process is performed on an actual substrate.
[0022] Namely, since the damage recovery process is performed on
the substrate having the OH group containing resin film, a damage
causing process such as etching, ashing and the like is not
required before the damage recovery process. Accordingly, the
sample preparation process becomes simple and, also, the processing
conditions can be inspected only by the damage recovery process.
Moreover, the film thickness of the OH group containing resin film
changes with high sensitivity in response to a change in the
processing conditions. Therefore, the processing conditions can be
inspected simply and precisely.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The above and other objects and features of the present
invention will become apparent from the following description of
embodiments, given in conjunction with the accompanying drawings,
in which:
[0024] FIG. 1 is a block diagram showing a silylation processing
system capable of performing a method of the present invention;
[0025] FIG. 2 describes a schematic cross sectional view of a
silylation processing apparatus of the silylation processing system
of FIG. 1;
[0026] FIG. 3 provides a flow chart showing a processing condition
inspection method of the silylation processing apparatus using the
silylation processing system of FIG. 1;
[0027] FIG. 4 illustrates results of measuring a film thickness
increase amount (film thickness difference) when a silylation
process is performed on a wafer having a G-line resist film and a
KrF resist film as a photoresist film containing OH groups;
[0028] FIG. 5 offers results of measuring a film thickness increase
amount (film thickness difference) when a silylation process is
performed on a wafer having a KrF resist film as a photoresist film
containing OH groups while varying concentration of a silylation
agent;
[0029] FIG. 6 presents a relationship between concentration
(dilution ratio) of TMSDMA which is indicated in a horizontal axis
and a film thickness increase amount (film thickness difference)
.DELTA.t of a KrF resist film and a capacitance recovery amount of
a low-k film which are indicated in vertical axes;
[0030] FIGS. 7A to 7D show a relationship between silylation
processing time and .DELTA.t, a relationship between a pressure in
a chamber and .DELTA.t, a relationship between concentration of a
silylation agent (TMSDMA) and .DELTA.t, and a relationship between
a temperature and .DELTA.t, respectively;
[0031] FIGS. 8A and 8B depict a relationship between a pressure in
a chamber and .DELTA.t of a KrF resist film and a relationship
between processing time and a TMSDMA partial pressure at each
pressure level in a chamber, respectively;
[0032] FIG. 9 illustrates a temperature increase curve of a wafer
at each pressure level in a chamber; and
[0033] FIG. 10 is a top view showing a schematic configuration of a
substrate processing system which includes a silylation processing
system for realizing the present invention and can perform etching,
ashing and silylation successively.
DETAILED DESCRIPTION OF THE EMBODIMENT
[0034] The embodiments of the present invention will be described
with reference to the accompanying drawings which form a part
hereof.
[0035] FIG. 1 is a block diagram showing a silylation processing
system capable of performing a method of the present invention.
[0036] A silylation processing system 100 performs a silylation
process as a damage recovery process on a low-k film formed as an
interlayer insulating layer on a semiconductor wafer W serving as a
substrate to be processed. Further, the silylation processing
system 100 includes a silylation processing apparatus 1 for
performing a silylation process, a film thickness measurement
device 2 for measuring a thickness of a photoresist film formed on
a test wafer used to inspect processing conditions of the present
embodiment, a loader 3 for mounting thereon a carrier accommodating
therein a plurality of wafers W, a transfer device 4 for
transferring the wafer W, and a control unit 5 for controlling each
of the above components.
[0037] The control unit 5 has a controller 6 having a micro
processer (computer) which is connected to and controls each of the
silylation processing apparatus 1, the film thickness measurement
device 2, the loader 3 and the transfer device 4. The controller 6
is connected to a user interface 7 including a keyboard for
inputting commands, a display for displaying an operational status
of the silylation processing system 100 and the like such that an
operator can manage the silylation processing system 100.
[0038] The controller 6 is also connected to a storage unit 8 which
stores control programs for controlling the respective components
of the silylation processing system 100, or programs (i.e.,
recipes) for performing predetermined processes in the silylation
processing system 100. The recipes are stored in a storage medium
of the storage unit 8. The storage medium may be a fixed storage
medium such as a hard disk, or a portable storage medium such as a
CD-ROM, a DVD and a flash memory. Further, the recipes can be
transmitted from another device via, e.g., a dedicated line. If
necessary, a certain recipe may be retrieved from the storage unit
92 in accordance with the commands inputted through the user
interface 91 and executed in the controller 6 such that a desired
process is performed under control of the controller 6.
[0039] The silylation processing apparatus 1 serving as the damage
recovering apparatus may have a configuration shown in a schematic
cross sectional view of FIG. 2. The silylation processing apparatus
1 has a chamber 21 accommodating therein the wafer W, and a wafer
mounting table 22 is installed at a lower portion of the chamber
21. A heater 23 is buried in the wafer mounting table 22, so that
the wafer W mounted on the wafer mounting table 22 can be heated to
a desired temperature. The wafer mounting table 22 is provided with
wafer lifting pins 24 which can be protruded from or retracted into
the wafer mounting table 22. The wafer lifting pins 24 can place
the wafer W at a predetermined position above and separated from
the wafer mounting table 22, when the wafer W is transferred to and
from the wafer mounting table 22.
[0040] The chamber 21 is provided with an inner vessel 25 which
defines a narrow processing space S for accommodating the wafer W.
A silylation agent (silylation gas) is supplied into this
processing space S. The inner vessel 25 has a gas inlet path 26
formed at its center and extending in a vertical direction.
[0041] An upper portion of the gas inlet 26 is connected to a gas
supply line 27. The gas supply line 27 is connected to a line 29
extending from a silylation agent supply source 28 for supplying a
silylation agent such as TMSDMA (N-Trimethylsilyldimethylamine),
DMSDMA (Dimethylsilyldimethylamine), TMDS
(1,1,3,3-Tetramethyldisilazane), TMSPyrole
(1-Trimethylsilylpyrole), BSTFA
(N,O-Bis(trimethylsilyl)trifluoroacetamide) and BDMADMS
(Bis(dimethylamino)dimethylsilane), and a line 31 extending from a
carrier gas supply source 30 for supplying a carrier gas such as Ar
or N.sub.2 gas. The line 29 is provided with a vaporizer 32 for
vaporizing the silylation agent, a mass flow controller 33 and an
opening/closing valve 34 disposed thereon in this order from the
silylation agent supply source 28.
[0042] The line 31 is provided with a mass flow controller 35 and
an opening/closing valve 36 disposed thereon in this order from the
carrier gas supply source 30. The silylation agent vaporized by the
vaporizer 32 is carried by the carrier gas and is supplied through
the gas supply line 27 and the gas inlet path 26 into the
processing space S defined by the inner vessel 25. When the process
is performed, the wafer W is heated by the heater 23 to a
predetermined temperature. In this case, the wafer temperature can
be controlled, for example, in a range from a room temperature to
300.degree. C.
[0043] An air inlet line 37 is installed to extend from the
atmosphere outside the chamber 21 to the inner vessel 25 inside the
chamber 21. The air inlet line 37 is provided with a valve 38. As
the valve 38 is opened, air is introduced into the processing space
S defined by the inner vessel 25 inside the chamber 21.
Accordingly, moisture supplied with the air facilitates a
silylation reaction.
[0044] A gate valve G is provided at a sidewall of the chamber 21.
While the gate valve G is opened, the wafer W is loaded into or
unloaded from the chamber 1. A load-lock chamber (not shown)
communicates with the chamber 21 via the gate valve G. The wafer is
transferred to the load-lock chamber maintained at an atmospheric
pressure by the transfer device 4 in the atmosphere. Then, the
load-lock chamber is evacuated to vacuum, and the wafer W is loaded
into the chamber 21 by a transfer unit (not shown) provided in the
load-lock chamber. When the wafer W is unloaded, a reverse
operation is performed.
[0045] Gas exhaust lines 40 are provided at a bottom peripheral
portion of the chamber 21. Thus, the inside of the chamber 21 can
be exhausted to a predetermined pressure by a vacuum pump (not
shown) through the gas exhaust lines 40. A cold trap 41 is disposed
on the gas exhaust lines 40. A baffle plate 42 is disposed between
an upper portion of the wafer mounting table 22 and the chamber
wall.
[0046] The film thickness measuring device 2 may employ a film
thickness measuring device generally used in this field, for
example, a device having a commercially available spectral
reflectance thickness gauge in a housing.
[0047] A silylation process for an actual wafer is performed to
recover damages of a low-k film by a silylation reaction using a
silylation agent (silylation gas), the damages being caused by
performing etching and ashing on a wafer having the low-k film as
an interlayer insulating film. To be specific, the low-k film is
reformed by replacing OH groups generated in the low-k film due to
the damages with silyl groups such as trimethyl silyl groups, thus
recovering the electrical characteristics and the like.
[0048] In the present embodiment, the processing conditions of the
silylation processing apparatus are inspected before an actual
wafer is processed. The detailed description thereof will be given
hereinafter.
[0049] The processing conditions of the silylation processing
apparatus need to be inspected by actually performing the
silylation process. However, as described above, the silylation
process serving as a damage recovery process is carried out by
replacing the OH groups generated by etching damages or ashing
damages with the silyl groups. The low-k film does not have OH
groups in an initial state, and the silylation reaction does not
take place. For that reason, in a conventional case, etching and
ashing processes are performed on a wafer having a low-k film to
prepare a sample having OH groups. Then, a silylation process is
performed on the sample and, then, a dilute hydrofluoric acid
treatment is performed thereon. Accordingly, a film thickness
variation or a CD variation of the low-k film is detected, thereby
inspecting the processing conditions.
[0050] However, when the processing conditions are inspected as
described above, a sample preparation process becomes complicated
and, also, the processing conditions of the silylation process
cannot be obtained independently. In addition, sensitivity is not
sufficient.
[0051] Thus, in the present embodiment, a silylation process is
performed on a wafer having a photoresist film containing OH groups
and, then, a film thickness difference of the film is detected. As
a consequence, the processing conditions can be inspected simply
and precisely.
[0052] FIG. 3 is a flow chart showing a processing condition
inspection method of the silylation processing apparatus using the
silylation processing system.
[0053] First of all, a carrier accommodating therein a test wafer
having a photoresist film containing OH groups is loaded on the
loader 3 (step S1). The photoresist film containing OH groups may
employ a G-line resist film or a KrF resist film.
[0054] Next, the test wafer is unloaded from the carrier on the
loader 3 by the transfer device 4, and then is transferred to the
film thickness measurement device 2. A film thickness of the
photoresist film containing the OH groups is measured by the film
thickness measurement device 2 (step S2).
[0055] Thereafter, the test wafer is transferred to the silylation
processing apparatus 1 by the transfer device 4, and a silylation
process serving as a damage recovery process is performed on the
test wafer (step S3). When the test wafer is loaded into the
silylation processing apparatus 1, first, the test wafer is
transferred to the load-lock chamber (not shown) and the pressure
is adjusted therein. Then, the test wafer is loaded into the
chamber 21 by the transfer unit (not shown) in the load-lock
chamber.
[0056] At this time, the conditions of the silylation process,
e.g., processing time, a pressure, concentration of silylation gas,
a temperature and the like, are set based on a predetermined recipe
for processing an actual wafer. For example, when a G-line resist
film is used as a photoresist film and TMSDMA is used as a
silylation agent (silylation gas), the reaction between the
photoresist film and the silylation agent takes place as will be
described later, and the film thickness of the photoresist film
increases.
##STR00001##
[0057] After the silylation process is carried out, the test wafer
is returned from the chamber 1 to the load-lock chamber. Then, the
load-lock chamber is open to the atmosphere and the test wafer is
transferred to the film thickness measurement device 2 by the
transfer device 4. Accordingly, the film thickness of the
photoresist film containing OH groups after the silylation process
is measured (step S4).
[0058] Thereafter, an operation unit of the controller 6 calculates
a film thickness difference (film thickness increase amount after
the silylation process) .DELTA.t between an initial film thickness
of the photoresist film, which was measured in step S2, and a film
thickness of the photoresist film after the silylation process,
which was measured in step S4 (step S5).
[0059] Next, it is determined whether the film thickness difference
.DELTA.t is within a tolerance range (step S6). Accordingly, it is
possible to determine whether the processing conditions of the
silylation processing apparatus 1 are appropriate or not.
[0060] If the film thickness difference .DELTA.t is within the
tolerance range, the silylation process for an actual wafer is
initiated (step S7). On the contrary, if .DELTA.t is not within the
tolerance range, the processing conditions are adjusted (step S8)
and, then, the silylation process is initiated.
[0061] The above-described inspection process can be controlled by
the control unit 5 as will be described hereinafter. After the
carrier accommodating therein the test wafer is loaded on the
loader 3 in step S1, the test wafer is transferred to the film
thickness measurement device 2 by controlling the transfer device
4. Next, the film thickness of the photoresist film measured in
step S2 is transmitted to the controller 6. After the silylation
process is completed, the test wafer is transferred to the film
thickness measurement device 2 by controlling the transfer device
4.
[0062] Then, the film thickness of the photoresist film after the
silylation process, which was measured in step S4, is transmitted
to the controller 6. The operation unit of the controller 6
calculates the film thickness difference .DELTA.t based on the
above data in step S5. By comparing .DELTA.t and a film thickness
difference corresponding to preset normal silylation processing
conditions, it is determined in step S6 whether or not .DELTA.t is
within a tolerance range. The result thereof is displayed on, e.g.,
the display of the user interface 7. When .DELTA.t is not within
the tolerance range, an alarm indicating abnormality can be
operated. When there is abnormality, the processing conditions can
be also adjusted by the instruction from the controller 6.
[0063] The film thickness of the photoresist film containing OH
groups, such as a G-line resist film or a KrF resist film,
increases after the silylation reaction between the OH groups and
the silylation agent (silylation gas). This is because the OH
groups are replaced with silyl groups. In the low-k film, a film
thickness increase amount after the silylation reaction is
extremely small.
[0064] On the contrary, in the photoresist film containing OH
groups, a film thickness variation is large and, also, a film
thickness difference can be achieved precisely and reproducibly by
varying the silylation processing conditions. Therefore, it is
possible to determine whether the silylation processing conditions
are appropriate or not by measuring the film thickness difference
.DELTA.t. In other words, the progress of the silylation reaction
changes depending on the silylation processing conditions, and it
is precisely and reproducibly reflected on a film thickness
difference before and after the silylation process of the
photoresist film. If the film thickness difference .DELTA.t is
within an appropriate range, it is determined that the silylation
processing conditions are normal. Otherwise, it is determined that
the silylation processing conditions are abnormal.
[0065] Hereinafter, results of actually measuring a film thickness
variation when the silylation process was performed on the
photoresist film containing OH groups will be explained.
[0066] FIG. 4 shows results of measuring a film thickness increase
amount (film thickness difference) .DELTA.t when a silylation
process was performed on a wafer having a G-line resist film and a
KrF resist film as a photoresist film containing OH groups. In this
case, the silylation process was performed under following
conditions: a pressure in the chamber at about 50 Torr (about 6666
Pa); TMSDMA serving as a silylation agent; a flow rate of about 500
sccm (mL/min); a stage temperature controlled at about 180.degree.
C.; and processing time of about 150 sec. Further, an optical
interferometric film thickness measurement device (trade mark:
NanoSpec 8300) was used as a film thickness measurement device
(same device was also used in the following).
[0067] As illustrated in FIG. 4, the average of the film thickness
increase amount .DELTA.t in the G-line resist film was about 437
nm, and that in the KrF resist film was about 189 nm. Namely, it
was found that the film thickness increased in both films. Further,
although the same silylation process was performed on wafers of
different lots, the same results were obtained with
reproducibility. Although the non-uniformity in both films was
within about .+-.5%, the non-uniformity of the KrF resist film was
smaller. From the above, it is considered that it is advantageous
to use a KrF resist film. Further, .DELTA.t was calculated by
considering shrinkage of the resist film due to the application of
heat during the silylation process. Namely, .DELTA.t was obtained
by adding a shrinkage value due to the heating to a difference
value between an initial film thickness and a film thickness
measured after the silylation. These are the same in the following
cases.
[0068] Next, it was checked whether it was possible to detect
changes in the concentration of the silylation agent. The results
thereof are shown in FIG. 5. FIG. 5 depicts results of measuring a
film thickness increase amount (film thickness difference) .DELTA.t
when a silylation process was performed on a wafer having a KrF
resist film as a photoresist film containing OH groups while
varying concentration of a silylation agent. In this case, the
silylation process was performed under following conditions: a
pressure in the chamber at about 50 Torr (about 6666 Pa); a stage
temperature controlled at about 180.degree. C.; and processing time
of about 150 sec. The silylation process was performed while TMSDMA
having a flow rate of about 500 sccm (mL/min) (TMSDMA 100%) was
independently supplied as a silylation agent. Further, the
silylation process was performed while a mixture of TMSDMA and
N.sub.2 gas having respective flow rates of about 40 sccm (mL/min)
and 4000 sccm (mL/min) (TMSDMA 1%) was supplied in a diluted state.
As shown in FIG. 5, the average of .DELTA.t in TMSDMA 100% was
about 248 nm, and the average of .DELTA.t in TMSDMA 1% was about
122 nm. It was checked that the film thickness increase amount
(film thickness difference) .DELTA.t changed depending on a
dilution ratio of TMSDMA. From the above, it was found that when
the gas supply system of the silylation processing apparatus had a
defect, the defect was detectable from the difference of the film
thickness increase amount (film thickness difference) .DELTA.t.
[0069] Next, while varying the dilution ratio of the silylation
agent among the silylation processing conditions, an experiment was
conducted to check the variation of the film thickness increase
amount (film thickness difference) .DELTA.t of the KrF resist film
and the variation of the capacitance recovery amount when a
silylation process is performed on a low-k film. The results
thereof are shown in FIG. 6. FIG. 6 illustrates a relationship
between concentration (dilution ratio) of TMSDMA which is indicated
in a horizontal axis and a film thickness increase amount (film
thickness difference) .DELTA.t of the KrF resist film and a
capacitance recovery amount of the low-k film which are indicated
in vertical axes.
[0070] In this case, the silylation process was performed under
following conditions: a pressure in the chamber at about 20 Torr
(about 2666 Pa); a stage temperature controlled at about
180.degree. C.; and processing time of about 30 sec. TMSDMA was
used as a silylation agent, and the silylation process was
performed while TMSDMA and N.sub.2 gas are supplied at flow rates
of 80/4000 sccm (mL/min), 40/4000 sccm (mL/min) and 20/4000 sccm
(mL/min) (concentrations of TMSDMA of about 0.2%, 0.4% and 0.8%),
respectively. As can be seen from FIG. 6, the tendency of the film
thickness increase amount (film thickness difference) .DELTA.t of
the KrF resist film is substantially the same as that of the
capacitance recovery amount. Further, it was found that the
capacitance recovery effect (damage recovery effect) obtained by
the silylation process was checked from the film thickness increase
amount (film thickness difference) .DELTA.t in the present
embodiment. In other words, it was seen that as .DELTA.t increased,
the damage recovery effect by the silylation process increased.
[0071] Next, the variation of the film thickness increase amount
(film thickness difference) .DELTA.t of the KrF resist film was
measured while varying various silylation processing conditions.
The results thereof are illustrated in FIGS. 7A to 7D. FIG. 7A
shows a relationship between silylation processing time and
.DELTA.t; FIG. 7B depicts a relationship between a pressure in the
chamber and .DELTA.t; FIG. 7C describes a relationship between
concentration (dilution ratio) of a silylation agent (TMSDMA) and
.DELTA.t; and FIG. 7D provides a relationship between a temperature
and .DELTA.t.
[0072] As depicted in FIGS. 7A, 7C and 7D, .DELTA.t increases as
the processing time, the concentration of a silylation agent and
the temperature increase. Further, the damage recovery effect
increases as the silylation processing time, the concentration of a
silylation agent and the temperature increase. Furthermore,
.DELTA.t is the same in both cases of the TMSDMA concentration of
10% and no dilution (TMSDMA 100%), so that the same damage recovery
effect can be obtained in both cases of the dilution ratio of 10%
or no dilution. Namely, even if the concentration of TMSDMA exceeds
10%, the effect is saturated. Therefore, it is preferable to use
TMSDMA having a dilution ratio of 10% in view of the cost.
[0073] As shown in FIG. 7B, the value of .DELTA.t does not change
even if the pressure in the chamber increases. Here, the pressure
was adjusted by N.sub.2 gas while maintaining the constant flow
rate of TMSDMA, and the molecular weight of TMSDMA is set to be the
same at each pressure level. From the above, it is expected that
.DELTA.t increases by increasing the pressure and the molecular
weight of the silylation agent.
[0074] Based on the above results, it is clear that the film
thickness increase amount (film thickness difference) .DELTA.t of
the photoresist film containing OH groups, which is measured after
the silylation process, reflects the changes of the silylation
processing conditions, and whether the silylation processing
conditions are appropriate or not can be determined by measuring
.DELTA.t. Moreover, the tendency of the variation of .DELTA.t in
accordance with the changes of the silylation processing conditions
is the same as that of the variation of the capacitance recovery
amount of the low-k film. Thus, the processing conditions of the
silylation process serving as a damage recovery process can be
optimized by using a technique for calculating the film thickness
increase amount (film thickness difference) .DELTA.t of the
photoresist film having OH groups after the silylation process.
[0075] In order to optimize the processing conditions, .DELTA.t is
obtained by performing a silylation process on a test wafer under
initial conditions based on a relationship between .DELTA.t and
various processing conditions which is stored in advance in the
storage unit 8 of the control unit 5. Then, the silylation
processing conditions are adjusted based on .DELTA.t so that the
film thickness difference can have a value corresponding to the
optimal silylation conditions.
[0076] However, in the conventional case, the silylation process
was performed by using an excessive amount of liquid chemical
without optimizing the silylation processing conditions by
collectively considering throughput, device characteristics, and
reactivity to temperatures, pressures and the like. Accordingly, it
was difficult to achieve a maximum reaction amount with a minimum
liquid chemical cost.
[0077] Based on the above fact, a process for optimizing the
silylation processing conditions will be described hereinafter.
[0078] First of all, it was found that that the film thickness of
the photoresist film containing OH groups increased when the
silylation processing temperature was higher than or equal to about
120.degree. C. Meanwhile, the heat resistant temperature of the
semiconductor device is about 350.degree. C. Therefore, it is
preferable that the silylation processing temperature is between
about 120.degree. C. and about 350.degree. C.
[0079] Next, the pressure in the chamber (gas pressure) in the
silylation process will be explained. In this case, a KrF resist
was used as a photoresist containing OH groups, and TMSDMA was used
as a silylation agent (silylation gas). The temporal variation of
the TMSDMA partial pressure and the relationship between the
pressure and the film thickness variation .DELTA.t of the KrF
resist film were obtained at varied pressures (N.sub.2
pressure+TMSDMA pressure) in the chamber of about 1.5 Torr (200
Pa), 5 Torr (667 Pa), 12.5 Torr (1666 Pa) and 50 Torr (6666 Pa)
under the following conditions: a TMSDMA partial pressure of about
0.75 Torr (100 Pa); a silylation processing temperature controlled
at about 180.degree. C.; and a total processing time of about 70
seconds. The results thereof are shown in FIGS. 8A and 8B.
[0080] FIG. 8A shows a relationship between the pressure in the
chamber and the film thickness variation of the KrF resist, and
FIG. 8B illustrates a temporal variation of the TMSDMA partial
pressure at each pressure level. As can be seen from FIGS. 8A and
8B, when the pressure in the chamber ranges from about 1.5 Torr to
12.5 Torr (about 200 Pa to 1666 Pa), it is possible to obtain
relatively high .DELTA.t and relatively high reactivity. Specially,
when the pressure in the chamber is about 5 Torr (667 Pa), it is
possible to obtain the highest .DELTA.t and the highest reactivity.
Meanwhile, when the pressure in the chamber is about 50 Torr (6666
Pa), a period of time, required for the pressure increase and the
vacuum evacuation, becomes longer. Therefore, it reduces a period
of time for which the silylation agent is maintained at a
predetermined partial pressure, and a reaction amount tends to be
small. As a consequence, it is preferable that the pressure in the
chamber is equal to or smaller than about 50 Torr (6666 Pa).
[0081] Meanwhile, a period of time required to increase the
temperature of the wafer to about 180.degree. C. was measured at
varied pressures in the chamber of about 0.5 Torr (66.7 Pa), 1.5
Torr (200 Pa), 3 Torr (400 Pa), 5 Torr (667 Pa) and 12.5 Torr (1666
Pa). The results thereof are shown in FIG. 9. As illustrated in
FIG. 9, when the pressure in the chamber is about 0.5 Torr (66.7
Pa), the heat conductivity is low and, hence, the temperature
increasing time becomes longer. On the contrary, when the pressure
in the chamber is larger than or equal to about 1.5 Torr (200 Pa),
it is possible to reduce the temperature increasing time. Also when
the pressure in the chamber is smaller than or equal to about 1.5
Torr, it is considered that the temperature increasing time can be
reduced. From the above, it is clear that the pressure in the
chamber is preferably larger than or equal to about 1 Torr (133
Pa), and more preferably larger than or equal to about 1.5 Torr
(200 Pa).
[0082] Next, a description is given of a substrate processing
system which has therein a silylation processing system for
implementing the present invention and can perform etching, ashing
and silylation processes successively.
[0083] The silylation process serving as a damage recovery process
is performed after an etching process and an ashing process are
completed. Therefore, it is preferable to perform the silylation
process successively after the etching process and the ashing
process without breaking a vacuum. Here, there will be described a
multi chamber type substrate processing system capable of
performing etching, ashing and silylation processes successively
without breaking a vacuum.
[0084] FIG. 10 is a top view showing a schematic structure of the
substrate processing system. This substrate processing system 200
processes a semiconductor wafer (substrate) W in which a
photoresist serving as an etching mask having a predetermined
circuit pattern is formed on a low-k film serving as an etching
target film by a photolithography process. Further, the substrate
processing system 200 includes etching units 51 and 52 for
performing plasma etching, an ashing unit 53 for performing ashing,
and a silylation processing unit 54. These units 51 to 54 are
respectively disposed corresponding to four sides of a hexagonal
wafer transfer chamber 55. The other two sides of the wafer
transfer chamber 55 are respectively connected to load-lock
chambers 56 and 57.
[0085] A wafer loading/unloading chamber 58 is connected to the
load-lock chambers 56 and 57 on their sides opposite to the wafer
transfer chamber 55. The wafer loading/unloading chamber 58 has
three ports 59, 60, and 61 on its side opposite to the load-lock
chambers 56 and 57, wherein three carriers C capable of containing
wafers W are mounted on the three ports, respectively. Further, the
silylation processing unit 54 has the same main parts as those of
the silylation processing apparatus 1 of FIG. 2.
[0086] The etching units 51 and 52, the ashing unit 53, the
silylation processing unit 54, and the load-lock chambers 56 and 57
are connected to the sides of the wafer transfer chamber 55
respectively through gate valves G, as shown in FIG. 10. Each of
the units 51 to 54 and the chambers 56 and 57 communicates with the
wafer transfer chamber 55 by opening the corresponding gate valve
G, and is blocked from the wafer transfer chamber 55 by closing the
corresponding gate valve G. Gate valves G are also disposed between
the load-lock chambers 56 and 57 and the wafer loading/unloading
chamber 58. Each of the load-lock chambers 56 and 57 communicates
with the wafer loading/unloading chamber 58 by opening the
corresponding gate valve G, and is blocked from the wafer
loading/unloading chamber 58 by closing the corresponding gate
valve G.
[0087] The wafer transfer chamber 55 is provided with a wafer
transfer unit 62 disposed therein, for transferring wafers W to and
from the etching units 51 and 52, the ashing unit 53, the
silylation processing unit 54, and the load-lock chambers 56 and
57. The wafer transfer unit 62 is disposed substantially at the
center of the wafer transfer chamber 55. The wafer transfer unit 62
includes two rotating and extending/retracting portions 63 which
are rotatable, extensible and contractible. Two blades 64a and 64b,
each blade for supporting a wafer W, are respectively connected to
the leading ends of the rotating and extending/retracting portions
63. The two blades 64a and 64b are connected to the rotating and
extending/retracting portions 63 to be arranged in opposite
directions. Further, the inside of the wafer transfer chamber 55
can be maintained at a predetermined vacuum level.
[0088] A carrier C containing wafers W or an empty carrier C may be
mounted directly on each of the three ports 59, 60 and 61 of the
wafer loading/unloading chamber 58. When the carrier C is mounted,
a shutter (not shown) is separated such that the carrier C
communicates with the wafer loading/unloading chamber 58 while
preventing inflow of outside air. Further, an alignment chamber 65
for performing alignment of a wafer W is disposed on one side of
the wafer loading/unloading chamber 58. In addition, a film
thickness measurement device 69 is installed at the side of the
wafer loading/unloading chamber 58 opposite to the alignment
chamber 65. The film thickness measurement device 69 has the same
configuration as that of the film thickness measurement device 2 of
FIG. 1.
[0089] The wafer loading/unloading chamber 58 is provided with a
wafer transfer unit 66 disposed therein, for transferring wafers W
to and from the carriers C and load-lock chambers 56 and 57. The
wafer transfer unit 66 has a multi-joint arm structure and can move
on a rail 68 in a direction in which the carriers C are arranged,
to transfer a wafer W placed on a hand 67 at its leading end. Each
of the components of the substrate processing system 200 is
controlled by a control unit 70. The control unit 70 has the same
configuration as that of the control unit 5 of FIG. 1.
[0090] In this substrate processing system, when an actual wafer is
processed, the wafer W unloaded from the carrier C is transferred
to the wafer transfer chamber 55 maintained at a vacuum state via
the load-lock chamber 56 or 57. Next, the etching process, the
ashing process and the silylation process are carried out
successively in the etching unit 51 or 52, the ashing unit 53 and
the silylation processing unit 54, respectively, without breaking a
vacuum. Before the actual wafer is processed, a carrier C
accommodating therein a test wafer having a photoresist film
containing OH groups is installed at one of the ports 59, 60 and
61. Then, the test wafer is transferred to the film thickness
measurement device 69 so that a film thickness thereof is measured.
Thereafter, the test wafer is loaded into the silylation processing
unit 54 by the wafer transfer unit 62 of the wafer transfer chamber
55 via the load-lock chamber 56 or 57, and the silylation process
is performed. Next, the test wafer that has been subjected to the
silylation process is transferred to the load-lock chamber 56 or 57
by the wafer transfer unit 62. The test wafer is unloaded by the
wafer transfer unit 66 and then is loaded into the film thickness
measurement device 69 to measure a film thickness after the
silylation process. Thereafter, the test wafer is returned to the
carrier C. This process is performed on a single test wafer or
various test wafers, and a film thickness increase amount (film
thickness difference) .DELTA.t after the silylation process is
calculated. In this manner, the processing conditions of the
silylation processing unit 54 are inspected.
[0091] The present invention can be variously modified without
being limited to the above embodiment. For example, in the above
embodiment, the present invention is applied to a damage recovery
process for a low-k film. However, it is not limited thereto, and
may be applied to any film having OH groups generated by damages.
Further, in the above embodiment, the present invention is applied
to a process for recovering damages from etching and ashing.
However, the present invention may be applied to a process for
recovering damages from etching or ashing, and may be applied to
another process such as a wet cleaning process or the like as long
as it is a process for recovering a film having OH groups generated
by damages. Moreover, a G-line resist film and a KrF resist film
are used as an example of the photoresist film containing OH groups
in the above embodiment. However, it is not limited to the
photoresist film, and may be a resin film containing OH groups.
[0092] Moreover, a silylation process is described as an example of
a damage recovery process in the above embodiment. However, it is
not limited thereto, and may be another process as long as a
reaction for replacing OH groups with CH.sub.3 groups and the like
can take place.
[0093] Further, in the above embodiment, the semiconductor wafer is
used as a substrate to be processed. However, the substrate to be
processed may be another substrate such as a substrate for use in
an FPD (flat panel display) or the like.
[0094] While the invention has been shown and described with
respect to the embodiments, it will be understood by those skilled
in the art that various changes and modification may be made
without departing from the scope of the invention as defined in the
following claims.
* * * * *