U.S. patent application number 11/305686 was filed with the patent office on 2006-05-04 for method for atomic layer deposition (ald) of silicon oxide film.
This patent application is currently assigned to Moohan Co., Ltd.. Invention is credited to Byoung Ha Cho, Jung Soo Kim, Yong Il Kim, Won Hyung Lee, Cheol Ho Shin, Sang Tae Sim.
Application Number | 20060090694 11/305686 |
Document ID | / |
Family ID | 36260364 |
Filed Date | 2006-05-04 |
United States Patent
Application |
20060090694 |
Kind Code |
A1 |
Cho; Byoung Ha ; et
al. |
May 4, 2006 |
Method for atomic layer deposition (ALD) of silicon oxide film
Abstract
The present invention relates to a method for forming silicon
oxide films on substrates using an atomic layer deposition process.
Specifically, the silicon oxide films are formed at low temperature
and high deposition rate via the atomic layer deposition process
using a Si.sub.2Cl.sub.6 source unlike a conventional atomic layer
deposition process using a SiCl.sub.4 source. The atomic layer
deposition apparatus used in the above process can be in-situ
cleaned effectively at low temperature using a HF gas or a mixture
gas of HF gas and gas containing --OH group.
Inventors: |
Cho; Byoung Ha; (Daejeon-si,
KR) ; Kim; Yong Il; (Chuncheongnam-do, KR) ;
Shin; Cheol Ho; (Chuncheongnam-do, KR) ; Lee; Won
Hyung; (Chuncheongnam-do, KR) ; Kim; Jung Soo;
(Chuncheongnam-do, KR) ; Sim; Sang Tae;
(Chuncheongnam-do, KR) |
Correspondence
Address: |
MILLS & ONELLO LLP
ELEVEN BEACON STREET
SUITE 605
BOSTON
MA
02108
US
|
Assignee: |
Moohan Co., Ltd.
Samsung Electronics, Co., Ltd.
|
Family ID: |
36260364 |
Appl. No.: |
11/305686 |
Filed: |
December 16, 2005 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10422252 |
Apr 23, 2003 |
|
|
|
11305686 |
Dec 16, 2005 |
|
|
|
Current U.S.
Class: |
117/104 |
Current CPC
Class: |
C23C 16/45531 20130101;
C30B 25/14 20130101; C30B 29/18 20130101; C23C 16/4405 20130101;
C23C 16/402 20130101; C23C 16/45534 20130101 |
Class at
Publication: |
117/104 |
International
Class: |
C30B 23/00 20060101
C30B023/00; C30B 25/00 20060101 C30B025/00; C30B 28/12 20060101
C30B028/12; C30B 28/14 20060101 C30B028/14 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 25, 2002 |
KR |
2002-22618 |
Claims
1. In a method for forming a silicon oxide film on a surface of a
substrate using an atomic layer deposition (ALD) process, the
improvement comprising the sequential steps of: (a) exposing a
substrate having --OH groups adsorbed on a surface thereof to a
first trimethylamine catalyst suitable for activating at least a
portion of the hydrogen of the --OH groups; (b) simultaneously with
and/or following step (a), exposing the substrate surface to a
first source of silicon and of chlorine to form an
oxygen/silicon/chlorine complex along the substrate surface; (c)
following step (b), exposing the substrate surface to a second
trimethylamine catalyst suitable for activating at least a portion
of the chlorine in the oxygen/silicon/chlorine complex along the
substrate surface; and (d) following step (c), exposing the
substrate surface to an oxygen source to react with the activated
chlorine to form a silicon oxide layer consisting essentially of
silicon dioxide with --OH groups along the substrate surface.
2. In the method according to claim 1, the further improvement
wherein the atomic layer deposition process is performed at a
temperature ranging from about 50 to 200.degree. C.
3. In the method according to claim 1, the further improvement
wherein the atomic layer deposition process is performed at a
temperature ranging from about 50 to 140.degree. C.
4. In the method according to claim 1, the further improvement
wherein the process steps (a) to (d) are repeatedly performed to
form a silicon oxide film having a desired thickness of multiple
atomic layers.
5. (canceled)
6. (canceled)
7. A method for forming a silicon oxide film on a substrate in a
reaction chamber, said method comprising the steps of: (a) exposing
a substrate having --OH groups adsorbed on a surface thereof to a
first trimethylamine catalyst to activate a hydrogen portion of the
--OH groups; (b) exposing the surface of the substrate to a first
source of silicon and of chlorine to perform a reaction in which
oxygen/silicon/chlorine complexes are formed; (c) exposing the
surface of the substrate to a second trimethylamine catalyst to
activate chlorine in the oxygen/silicon/chlorine complexes; and,
(d) exposing the surface of the substrate to an oxygen source to
perform a reaction [4, where the reaction 4 is
O--Si--Cl*+H.sub.2O.fwdarw..about.O--Si--OH+HCl] in which the
activated chlorine reacts to leave a surface layer consisting
essentially of silicon dioxide with --OH groups adsorbed
thereon.
8. The method according to claim 7, wherein the steps (b) and (d)
are performed at a temperature ranging from about 50 to 200.degree.
C., respectively.
9. The method according to claim 7, wherein the steps (a) through
(d) are repeated two or more times.
10. (canceled)
11. The method according to claim 7, further comprising the step of
removing residual gases from the reaction chamber by pumping or
purging prior to performing step (c).
12. The method according to claim 7, further comprising the step of
removing residual gases from the reaction chamber by pumping or
purging after performing step (d).
13. The method according to claim 7, further comprising the step of
performing in-situ cleaning of the reaction chamber after step
(d).
14. The method according to claim 13, wherein the in-situ cleaning
is performed at a temperature ranging from about 50 to 200.degree.
C.
15. (canceled)
16. The method according to claim 13, wherein the in-situ cleaning
is performed using a HF gas or a gas mixture consisting essentially
of HF gas and gas containing --OH group.
17. The method according to claim 16, wherein the gas containing
--OH group is H.sub.2O or H.sub.2O.sub.2.
18. In a method for forming a silicon oxide film on a surface of a
substrate in a reaction chamber using an atomic layer deposition
(ALD) process, the improvement comprising the sequential steps of:
(a) exposing a substrate having --OH groups adsorbed on a surface
thereof to a first trimethylamine catalyst suitable for activating
at least a portion of the hydrogen of the --OH groups; (b)
simultaneously with and/or following step (a), exposing the
substrate surface to a first source of silicon and of chlorine to
form an oxygen/silicon/chlorine complex along the substrate
surface; (c) following step (b), exposing the substrate surface to
a second trimethylamine catalyst suitable for activating at least a
portion of the chlorine in the oxygen/silicon/chlorine complex
along the substrate surface; and, (d) following step (c), exposing
the substrate surface to an oxygen source to react with the
activated chlorine to form a silicon oxide layer consisting
essentially of silicon dioxide with --OH groups along the substrate
surface; (e) repeating steps (a) to (d) one or more additional
times to form a silicon oxide thin film comprising multiple atomic
layers, each consisting essentially of silicon dioxide; and, (f)
performing in-situ cleaning of the reaction chamber at a
temperature of about 50.degree. C. to about 200.degree. C.
19. In the method of claim 18, the further improvement wherein the
in-situ cleaning step (f) is performed using HF gas or a gas
mixture consisting essentially of HF gas and gas containing --OH
group in suitable proportions for effecting cleaning of the
reaction chamber.
20. In the method of claim 1, the further improvement wherein said
oxygen source is H.sub.2O.
21. The method according to claim 7, wherein said oxygen source is
H.sub.2O.
22. In the method of claim 18, the further improvement wherein said
oxygen source is H.sub.2O.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 10/422,252, filed on Apr. 23, 2003, which relies for priority
upon Korean Patent Application No. 10-2002-22618, filed on Apr. 25,
2002, the contents of which are herein incorporated by reference in
their entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention generally relates to methods for
forming silicon oxide films on substrates via atomic layer
deposition (hereinafter, referred to as `ALD`) processes, and more
specifically, to a method for forming a silicon oxide film at low
temperature and high deposition rate using Si.sub.2Cl.sub.6
(hexachloro disilane; hereinafter, referred to as `HCD`) and
H.sub.2O sources, and catalysts.
[0004] 2. Description of the Prior Art
[0005] Generally, a silicon oxide film is one of the most commonly
used thin films in a semiconductor since it provides superior
interface with silicon and has excellent dielectric
characteristics. There are two conventional methods for depositing
a silicon oxide film: (1) oxidation process wherein silicon is
oxidized at a temperature of more than 1000.degree. C.; and (2) a
Chemical Vapor Deposition (CVD) process wherein more than two
sources are provided at a temperature ranging from 600 to
800.degree. C. These methods cause diffusion on interface due to
high deposition temperature, thereby degrading electrical
characteristics of devices.
[0006] As semiconductor devices having memory capacity of more than
giga bytes are currently required to be manufactured, thin films
used in semiconductor devices should be controlled at the atomic
layer level. Further, the thin films are required to have excellent
step coverage and low deposition temperature to prevent diffusion
and oxidation at the interfaces. To satisfy the requirements, an
atomic layer deposition process has been proposed.
[0007] Conventionally, the silicon oxide film is deposited at a
temperature of more than 600K via the atomic layer deposition
process using SiCl.sub.4 and H.sub.2O sources. The conventional
deposition process is as follows.
[0008] First, a SiCl.sub.4 source is provided in a reaction chamber
containing a substrate having hydroxyl group (--OH)s on its
surface. The SiCl.sub.4 source reacts with the hydroxyl group, and
--SiCl3 is adsorbed on the surface of the substrate, HCl
by-products are formed (see Reaction Formula 1). When the reaction
of SiCl.sub.4 with the hydroxyl group is saturated, the remaining
SiCl.sub.4 no longer reacts (self-limiting condition), and the
surface of the substrate has --SiCl3 surface chemical species
adsorbed thereon. --OH*+SiCl.sub.4.fwdarw.--O--Si--Cl*.sub.3+HCl
[Reaction Formula 1]
[0009] When the above reaction is complete, the H2O source is
provided to the reactor chamber. The H.sub.2O source reacts with
the --SiCl3 surface chemical species to generate adsorption of the
hydroxyl group thereto and HCl by-products (see Reaction Formula
2). When the reaction of H.sub.2O with the --SiCl3 surface chemical
species is saturated, the remaining H.sub.2O no longer reacts
(self-limiting condition), and the surface of the substrate has
hydroxyl groups adsorbed thereon.
--O--Si--Cl*+H.sub.2O.fwdarw.--O--Si--OH*+HCl [Reaction Formula
2]
[0010] The above-described process is repeated to deposit the
silicon oxide film. However, the conventional method requires high
temperature of more than 600K, long time necessary for deposition
and a large amount of sources.
[0011] In order to solve the foregoing problems, a method for
forming silicon oxide films at a temperature below 200.degree. C.
using catalysts and small amount of sources is disclosed in U.S.
Pat. No. 6,090,442. The disclosed method uses catalysts, which
allows silicon oxide to be deposited even at a temperature below
200.degree. C. However, the disclosed method has the following
problems.
[0012] First, when a silicon oxide film is deposited at a
temperature ranging from room temperature to 50.degree. C., the
by-products from the reaction and unreacted liquid sources such as
HCD and H.sub.2O are not easily removed due to low temperature in
the reactor chamber. These materials exist as particles in the thin
film after deposition, which deteriorate properties of the thin
film.
[0013] Second, when a silicon oxide film is deposited at a
temperature above 50.degree. C., by-products resulting from
reaction and unreacted liquid sources such as HCD and H.sub.2O are
easily removed. However, the deposition rate of thin film is very
low. That is, when a silicon oxide film is deposited using
SiCl.sub.4, H.sub.2O and catalysts at a temperature above
50.degree. C., the deposition rate is lower than 1.0 .ANG. per
cycle (see FIG. 1). As a result, the yield of device is
reduced.
[0014] When a silicon oxide film is deposited via the above
conventional atomic layer deposition process, residuals are
generated in a reactor chamber during the formation process by a
plurality of reaction gases. These residuals are adsorbed to a
heater, a disc, and an outside wall and an upper surface of reactor
chamber as well as the substrate. The residuals in the atomic layer
deposition reactor are removed by in-situ cleaning which uses
thermal or plasma method using NF.sub.3 gas. The cleaning method is
used in deposition process of silicon oxide film performed at
temperature above 400.degree. C.
[0015] As a result, when a silicon oxide film is deposited via the
atomic layer deposition process at low temperature below
400.degree. C., in-situ cleaning cannot be performed.
SUMMARY OF THE INVENTION
[0016] It is an object of the present invention to provide a method
for forming a silicon oxide film at low temperature and a high
deposition rate via an atomic layer deposition process.
[0017] In order to achieve the above-described object, the method
for forming a silicon oxide film via an atomic layer deposition
process employs a HCD source to improve the deposition rate instead
of the conventional SiCl.sub.4 source.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a graph illustrating the deposition rate of
silicon oxide film depending on the reaction temperature during the
conventional ALD process using a SiCl.sub.4 source.
[0019] FIG. 2 is a reaction scheme illustrating the mechanism of
depositing a silicon oxide film using a Si.sub.2Cl.sub.6
source.
[0020] FIG. 3 illustrates the structures of SiCl.sub.4 and
Si.sub.2Cl.sub.6.
[0021] FIG. 4 is a graph illustrating the deposition rate of
silicon oxide film depending on the amount of Si.sub.2Cl.sub.6
source during the ALD process of the present invention.
[0022] FIG. 5 is a graph illustrating the deposition rate of
silicon oxide film depending on the reaction temperature during the
ALD process of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] The method in accordance with the present invention for
forming a silicon oxide film via the atomic layer deposition
process using the HCD source comprises:
[0024] (a) exposing a substrate having --OH groups adsorbed on the
surface thereof to a first catalyst to activate hydrogen;
[0025] (b) exposing the surface of the substrate to a first source
of Si.sub.2Cl.sub.6 to perform a reaction 3, where the reaction 3
is
--OH*+Si.sub.2Cl.sub.6.fwdarw.--O--Si.sub.2Cl.sub.5/--O--Si.sub.2Cl.sub.4-
+HCl;
[0026] (c) exposing the surface of the substrate to a second
catalyst to activate chlorine; and
[0027] (d) exposing the surface of the substrate to a second source
of H.sub.2O to perform a reaction 4, where the reaction 4 is
--O--Si--Cl*+H.sub.2O.fwdarw.--O--Si--OH+HCl.
[0028] The above process will be described in detail with reference
to FIG. 2.
[0029] HCD gas and a catalyst are provided on the surface of a
substrate having hydroxyl groups adsorbed thereon. The catalyst
activates the hydroxyl group adsorbed on the surface. The activated
hydroxyl group reacts with the HCD source, and --Si.sub.2Cl.sub.4
or --Si.sub.2Cl.sub.5 is adsorbed to the surface of the substrate
and by-products are generated. The activated surface-adsorbed
groups react with the provided H.sub.2O source, resulting in
generation of HCl as by-products and adsorption of the hydroxyl
group to --Si.sub.2Cl.sub.4 or --Si.sub.2Cl.sub.5. When the
reaction of H.sub.2O with the activated surface-adsorbed group is
saturated, remaining H.sub.2O no longer reacts (self-limiting
condition).
[0030] The HCD and H.sub.2O sources used in the present invention
are required to be alternately provided to the reactor chamber.
They should not be in the reactor chamber simultaneously.
Therefore, when no more reactions occur in each step of providing
sources, the pressure of the reactor chamber is decreased to a
pressure below 1 Torr by pumping, or purge process is performed
using inert gas, or pumping and purging are performed
simultaneously to remove residual sources and by-products from the
chamber.
[0031] Foregoing processes constitute a cycle to form multiple
layers of thin films, and the cycle may be repeated. That is, a
silicon oxide film can be formed by repeating the steps (a) through
(d) to have a desired thickness.
[0032] The method of the present invention provides a high
deposition ratio due to difference in structures of SiCl.sub.4 and
HCD (see FIG. 3). --SiCl.sub.3 is adsorbed to the surface of the
substrate when the silicon oxide film is deposited using SiCl.sub.4
while --Si.sub.2Cl.sub.4 or --Si.sub.2Cl.sub.5 is adsorbed to the
surface of the substrate when the silicon oxide film is deposited
using HCD. That is, one Si atom is adsorbed to the surface when
SiCl.sub.4 is used while two Si atoms are adsorbed to the surface
when HCD is used. As a result, when the HCD source is used, a
deposition ratio is about two times higher than that of when the
SiCl.sub.4 source is used.
[0033] The above-described ALD process is performed at low
temperature ranging from 50 to 200.degree. C., preferably from 50
to 140.degree. C., using catalysts which are Lewis bases such as
pyridine, trimethylamine (TMA) or triethylamine (TEA) to improve
efficiency of deposition at low temperature.
[0034] The reason for performing the atomic layer deposition
process at a temperature above 50.degree. C. is to prevent
deterioration of properties of thin films. When silicon oxide films
are deposited at a temperature ranging from room temperature to
50.degree. C., a porous thin film is formed, which deteriorates
properties of thin film. In addition, by-products resulting from
the reaction and unreacted liquid sources are not easily removed
due to the low temperature of the chamber, which exist as particles
in the thin film, thereby degrading properties of the thin
films.
[0035] It is preferable that the ALD process is performed in the
chamber under a pressure ranging from 1 mTorr to 10 Torr.
[0036] When the formation of thin film is complete, the reactor
chamber in-situ cleaning can be effectively performed using a HF
gas or a mixture gas of HF gas and gas containing --OH group as
cleaning gas at a temperature similar to the deposition temperature
of silicon oxide film.
[0037] The --OH group in the silicon oxide film deposited at low
temperature via the atomic layer deposition process using a
catalyst serves as a catalyst when a HF gas is injected. As a
result, the HF gas is decomposed into fluorine and hydrogen due to
the catalyst function of the --OH group. The silicon oxide film
reacts with the decomposed fluorine to form SiF.sub.4 as
by-products, which easily removed.
[0038] When mixture gas of H.sub.2O or H.sub.2O.sub.2 gas which
contains --OH group and HF gas is used in the in-situ cleaning of
the atomic layer deposition apparatus, more HF gas is decomposed
into fluorine and hydrogen to improve efficiency of in-situ
cleaning.
[0039] The in-situ cleaning comprises the following steps
(a)-(d):
[0040] (a) Wafers positioned on a susceptor for loading at least
one wafer are conveyed out of the chamber after the completion of
formation process;
[0041] (b) a cleaning atmosphere is prepared in the chamber by
maintaining the temperature therein at the deposition
temperature;
[0042] (c) residuals, impurities and films deposited on undesired
portions of the chamber are cleaned under the cleaning atmosphere
by providing a HF gas or a mixture gas of HF gas and gas containing
--OH group as cleaning gas; and
[0043] (d) by-products and impurities generated during the cleaning
process are removed out of the chamber by injecting inert gas.
[0044] The in-situ cleaning is performed at the same temperature as
the ALD process or within .+-.10% margin of the temperature. In
this manner, in-situ cleaning is possible for low temperature ALD
apparatus.
[0045] Hereinafter, the preferred embodiments will be described in
detail. However, it should be noted that the scope of the present
invention is not limited to the preferred embodiments.
EXAMPLE 1
Variation in Deposition Rate of Silicon Oxide Film Depending on
Increase in Amount of HCD Source
[0046] The following experiment was conducted to find out the
deposition rate of silicon oxide film depending on the increase in
the amount of HCD source. HCD where the flow rate varies as shown
in FIG. 4 and pyridine having a flow rate of 100 sccm were provided
to a chamber. Residual sources in the chamber were then removed by
pumping until the pressure reaches 1 mTorr. Thereafter, H2O having
a flow rate of 500 sccm and pyridine having a flow rate of 100 sccm
were provided to the chamber, and the residual sources were again
removed by pumping until the pressure reaches 1 mTorr. Above
processes were repeated to form a silicon oxide film.
[0047] As shown in FIG. 4, the deposition rate increased as the
amount of HCD source increased. The deposition rate was saturated
at 2 .ANG./cycle. The saturation occurs due to self-limiting
condition of HCD and chemical species adsorbed to the surface of
the substrate.
EXAMPLE 2
Variation of Deposition Rate of Silicon Oxide Film Depending on
Deposition Temperature
[0048] The following experiment was conducted to find out the
deposition rate of silicon oxide film depending on deposition
temperature. For the comparison with U.S. Pat. No. 6,090,422
wherein SiCl.sub.4 is used, the experiment was conducted at the
temperature similar to that of U.S. Pat. No. 6,090,422 shown in
FIG. 1. HCD having a flow rate of 500 sccm and pyridine having a
flow rate of 100 sccm were provided to a chamber. Residual sources
in the chamber were then removed by pumping until the pressure
reaches 1 mTorr. Thereafter, H.sub.2O having a flow rate of 500
sccm and pyridine having a flow rate of 100 sccm were provided to
the chamber, and the residual sources were again removed by pumping
until the pressure reaches 1 mTorr. Above processes were repeated
to form a silicon oxide film.
[0049] As shown in FIG. 5, the deposition rate of silicon oxide
film decreased as the deposition temperature increased. However,
when the deposition rate shown in FIG. 5 was compared with that
shown in FIG. 1, the deposition rate (.ANG./cycle) of the present
invention was about 1.5 to 2.0 times higher than that shown in FIG.
1 under the temperatures ranging from 320 to 370K, that is, 50 to
100.degree. C.
[0050] As discussed earlier, according to the present invention,
the ALD process allows silicon oxide films to be formed at low
temperature and at higher deposition rate using the HCD source,
thereby increasing production of wafers.
[0051] Additionally, in-situ cleaning for the ALD apparatus can be
performed at low temperature below 200.degree. C. using a HF gas or
a mixture gas of HF gas and gas containing --OH group, thereby
improving uniformity and reproducibility of wafer and properties of
film formed thereon. As a result, the yield of wafers is
improved.
* * * * *