U.S. patent application number 09/867869 was filed with the patent office on 2002-12-19 for method of forming a carbon doped oxide layer on a substrate.
Invention is credited to Andideh, Ebrahim, Peterson, Kevin L..
Application Number | 20020192982 09/867869 |
Document ID | / |
Family ID | 25350631 |
Filed Date | 2002-12-19 |
United States Patent
Application |
20020192982 |
Kind Code |
A1 |
Andideh, Ebrahim ; et
al. |
December 19, 2002 |
METHOD OF FORMING A CARBON DOPED OXIDE LAYER ON A SUBSTRATE
Abstract
A method of forming a carbon doped oxide layer on a substrate is
described. That method comprises introducing into a chemical vapor
deposition apparatus a precursor gas that is selected from those
having the formula (CH.sub.3).sub.xSi(OCH3).sub.4-x.
Simultaneously, a background gas, oxygen and nitrogen are
introduced into the chemical vapor deposition apparatus. That
apparatus is then operated under conditions that cause a carbon
doped oxide layer to form on the substrate.
Inventors: |
Andideh, Ebrahim; (Portland,
OR) ; Peterson, Kevin L.; (Hillsboro, OR) |
Correspondence
Address: |
Michael A. Bernadicou
BLAKELY, SOKOLOFF, TAYLOR & ZAFMAN LLP
Seventh Floor
12400 Wilshire Boulevard
Los Angeles
CA
90025-1026
US
|
Family ID: |
25350631 |
Appl. No.: |
09/867869 |
Filed: |
May 29, 2001 |
Current U.S.
Class: |
438/780 ;
257/E21.277 |
Current CPC
Class: |
C23C 16/401 20130101;
H01L 21/02216 20130101; H01L 21/02274 20130101; H01L 21/31633
20130101; H01L 21/02126 20130101 |
Class at
Publication: |
438/780 |
International
Class: |
H01L 021/36 |
Claims
What is claimed is:
1. A method of forming a carbon doped oxide layer on a substrate
comprising: introducing into a chemical vapor deposition apparatus
a precursor gas that is selected from the group consisting of gases
that have the formula (CH.sub.3).sub.xSi(OCH3).sub.4-x;
simultaneously introducing a background gas, oxygen and nitrogen
into the chemical vapor deposition apparatus; then operating the
apparatus under conditions that cause a carbon doped oxide layer to
form on the substrate.
2. The method of claim 1 wherein the chemical vapor deposition
apparatus is a plasma enhanced chemical vapor deposition
reactor.
3. The method of claim 2 wherein the resulting carbon doped oxide
has a dielectric constant that is less than or equal to about
3.0.
4. The method of claim 3 wherein the precursor gas is selected from
the group consisting of tetramethoxysilane, methyltrimethoxysilane,
dimethyidimethoxysilane, and trimethylmethoxysilane.
5. The method of claim 4 wherein the background gas comprises an
inert gas.
6. The method of claim 5 wherein the background gas comprises
helium and further comprising: introducing the precursor gas into
the plasma enhanced chemical vapor deposition reactor at a rate of
between about 90 and about 200 sccm; introducing the background gas
into the plasma enhanced chemical vapor deposition reactor at a
rate of between about 20 and about 200 sccm; introducing oxygen
into the plasma enhanced chemical vapor deposition reactor at a
rate of between about 1 and about 20 sccm; and introducing nitrogen
into the plasma enhanced chemical vapor deposition reactor at a
rate of between about 15 and about 300 sccm.
7. The method of claim 6 wherein nitrogen and oxygen are introduced
into the plasma enhanced chemical vapor deposition reactor at a
flow rate ratio that is between about 1:1 and about 20:1.
8. The method of claim 7 wherein the carbon doped oxide is
deposited on the substrate at a rate that exceeds about 7,000
angstroms per minute.
9. A method of forming a semiconductor device comprising: forming
on a substrate a carbon doped oxide layer by introducing into a
plasma enhanced chemical vapor deposition reactor a precursor gas
that is selected from the group consisting of tetramethoxysilane,
methyltrimethoxysilane, dimethyldimethoxysilane, and
trimethylmethoxysilane; simultaneously introducing a background
gas, oxygen and nitrogen into the plasma enhanced chemical vapor
deposition reactor; then operating the reactor under conditions
that cause a carbon doped oxide layer to form on the substrate at a
rate that exceeds about 7,000 angstroms per minute.
10. The method of claim 9 wherein the background gas comprises
helium, which is added to the nitrogen and oxygen that is fed into
the reactor.
11. The method of claim 10 further comprising: introducing the
precursor gas into the plasma enhanced chemical vapor deposition
reactor at a rate of between about 90 and about 200 sccm;
introducing the background gas into the plasma enhanced chemical
vapor deposition reactor at a rate of between about 20 and about
200 sccm; introducing oxygen into the plasma enhanced chemical
vapor deposition reactor at a rate of between about 1 and about 20
sccm; and introducing nitrogen into the plasma enhanced chemical
vapor deposition reactor at a rate of between about 15 and about
300 sccm.
12. The method of claim 11 wherein nitrogen and oxygen are
introduced into the plasma enhanced chemical vapor deposition
reactor at a flow rate ratio that is between about 1:1 and about
20:1.
13. A method of forming a semiconductor device comprising: forming
on a substrate a carbon doped oxide layer by introducing into a
plasma enhanced chemical vapor deposition reactor at a rate of
between about 90 and about 200 sccm a precursor gas that is
selected from the group consisting of tetramethoxysilane,
methyltrimethoxysilane, dimethyldimethoxysilane, and
trimethylmethoxysilane; simultaneously introducing helium at a rate
of between about 20 and about 200 sccm, oxygen at a rate of between
about 1 and about 20 sccm, and nitrogen at a rate of between about
15 and about 300 sccm into the plasma enhanced chemical vapor
deposition reactor; then operating the reactor under conditions
that cause a carbon doped oxide layer to form on the substrate.
14. The method of claim 13 wherein nitrogen and oxygen are
introduced into the plasma enhanced chemical vapor deposition
reactor at a flow rate ratio that is between about 1:1 and about
20:1.
15. The method of claim 14 wherein the carbon doped oxide is
deposited at a rate that exceeds about 7,000 angstroms per minute.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method of forming a
carbon doped oxide layer on a substrate, when making a
semiconductor device.
BACKGROUND OF THE INVENTION
[0002] Semiconductor devices include metal layers that are
insulated from each other by dielectric layers. As device features
shrink, reducing the distance between the metal layers and between
metal lines on each layer, capacitance increases. To address this
problem, insulating materials that have a relatively low dielectric
constant are being used in place of silicon dioxide to form the
dielectric layer that separates the metal lines.
[0003] A material that may be used to form such a low k dielectric
layer is carbon doped oxide ("CDO"). Using this material instead of
silicon dioxide to separate metal lines may yield a device having
reduced propagation delay, cross-talk noise and power dissipation.
A CDO layer may be deposited on a substrate using a plasma enhanced
chemical vapor deposition ("PECVD") process. When using such a
process to form such a layer, gases that provide a source of
silicon, oxygen, and carbon must be fed into a PECVD reactor.
Examples of such gases include those having the formula
(CH.sub.3).sub.xSi(OCH3).sub.4-x, e.g., tetramethoxysilane,
methyltrimethoxysilane, dimethyldimethoxysilane, and
trimethylmethoxysilane. A background gas, e.g., an inert gas such
as helium, may be fed into the reactor at the same time. That
reactor may then be operated at conventional pressures,
temperatures, RF and power for a time sufficient to deposit a CDO
layer of the desired thickness onto the substrate.
[0004] Although processes that use (CH.sub.3).sub.xSi(OCH3).sub.4-x
precursors to form CDO layers may produce layers that have a
dielectric constant that is less than 3.0, those processes generate
those layers at a relatively low deposition rate. Accordingly,
there is a need for an improved process for making a CDO insulating
layer. There is a need for such a process that generates a CDO
layer from a (CH.sub.3).sub.xSi(OCH3)- .sub.4-x precursor at an
increased deposition rate. The method of the present invention
provides such a process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 provides a schematic representation of a CVD chamber
for a PECVD reactor.
[0006] FIG. 2 represents a cross-section of a structure that
includes a CDO layer deposited on a substrate, which may be
generated when forming a semiconductor device.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0007] A method is described for forming a carbon doped oxide layer
on a substrate. That method comprises introducing into a chemical
vapor deposition apparatus a precursor gas that is selected from
the group consisting of gases that have the formula
(CH.sub.3).sub.xSi(OCH3).sub.4-- x. Simultaneously, a background
gas, oxygen and nitrogen are introduced into the chemical vapor
deposition apparatus, which is then operated under conditions that
cause a carbon doped oxide layer to form on the substrate.
[0008] In the following description, a number of details are set
forth to provide a thorough understanding of the present invention.
It will be apparent to those skilled in the art, however, that the
invention may be practiced in many ways other than those expressly
described here. The invention is thus not limited by the specific
details disclosed below.
[0009] In the method of the present invention, a substrate, e.g., a
silicon wafer upon which various conducting and insulating layers
may have been formed, is placed in a chemical vapor deposition
apparatus--preferably a PECVD reactor, e.g., PECVD reactor 100
illustrated in FIG. 1. To form a CDO layer on such a substrate, in
accordance with the method of the present invention, gases that
provide a source of carbon, silicon, and oxygen are introduced into
reactor 100 in the conventional manner.
[0010] Gases that may provide a source of these elements include
those that have the formula (CH.sub.3).sub.xSi(OCH3).sub.4-x. Such
gases include those that contain tetramethoxysilane,
methyltrimethoxysilane, dimethyidimethoxysilane, and/or
trimethylmethoxysilane. A particularly preferred precursor gas is
dimethyidimethoxysilane. Note that while these substances are
introduced into the reactor as gases, they may be liquids at
standard temperature and pressure.
[0011] At the same time the gas that provides this source of
silicon, carbon, and oxygen is fed into the reactor, a background
gas, e.g., an inert gas such as helium, is fed into the reactor. In
the method of the present invention, oxygen and nitrogen are also
introduced into the reactor. These gases may be introduced at the
following flow rates:
1 Precursor gas flow rate 90-200 sccm Background gas flow rate
20-200 sccm Oxygen gas flow rate 1-20 sccm Nitrogen gas flow rate
15-300 sccm
[0012] Although these gases are preferably introduced into the
reactor at the flow rates specified above, they may, of course, be
fed into the reactor at flow rates that fall outside the indicated
ranges, without departing from the spirit and scope of the present
invention. Those gases may be introduced into reactor 100 at
conventional temperatures and pressures. Optimal operating
conditions may, of course, depend upon the composition of the gas
streams fed into the reactor, the type of reactor used, and the
desired properties for the resulting CDO layer. A CDO layer with
acceptable properties may be formed by maintaining the reactor
pressure between about 2.0 and about 10.0 Torr (more preferably
between about 3.0 and about 6.0 Torr), the susceptor temperature
between about 350.degree. C. and about 450.degree. C., and the
electrode spacing at between about 15 and about 50 mm (more
preferably between about 24 and about 26 mm). To generate a plasma
from such a mixture of gases, RF energy is applied--preferably at
standard frequencies and at between about 1,600 and about 1,800
watts.
[0013] In a particularly preferred embodiment of the present
invention, oxygen and nitrogen are introduced into the reactor such
that they constitute, in combination, less than about 5% of the
total gas flow. For optimum results, the nitrogen and oxygen should
be fed into the reactor at a flow rate ratio that is between about
1:1 and about 20:1. Feeding into reactor 100 this combination of
precursor and background gases along with oxygen and nitrogen,
under the above specified operating conditions, should cause CDO
layer 200 to form on substrate 201 (as illustrated in FIG. 2) such
that CDO layer 200 has a dielectric constant that is less than or
equal to about 3.0.
[0014] The process of the present invention may enable the
generation of a CDO layer that has a slightly lower dielectric
constant, when compared to the dielectric constant of CDO layers
made from processes that apply a (CH.sub.3).sub.xSi(OCH3).sub.4-x
precursor gas without oxygen and nitrogen. In addition, the process
of the present invention enables a CDO layer to be deposited on a
substrate at a rate that exceeds about 7,000 angstroms per minute.
Increasing that deposition rate enhances the manufacturability of
processes for making semiconductor devices that include CDO
insulating layers.
[0015] Although the foregoing description has specified certain
steps, materials, and equipment that may be used in the above
described method for forming a CDO layer on a substrate, those
skilled in the art will appreciate that many modifications and
substitutions may be made. Accordingly, it is intended that all
such modifications, alterations, substitutions and additions be
considered to fall within the spirit and scope of the invention as
defined by the appended claims.
* * * * *