Dual inlaid process using a bilayer resist

Details Dual inlaid process using a bilayer resist Dual inlaid process using a bilayer resist

2001-04-04

2003-07-08

Huff, Mark F. (Department: 1756)

Radiation imagery chemistry: process, composition, or product th

Imaging affecting physical property of radiation sensitive...

Making electrical device

C430S312000, C430S313000, C430S314000, C430S322000, C438S636000

Reexamination Certificate

active

06589711

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention is related generally a method of making a semiconductor device and specifically to a dual damascene process using a bilayer resist.
In order to increase the miniaturization of semiconductor devices, contacts between conductive layers in a semiconductor device are formed by the dual damascene process which utilizes a dual inlaid via. It has recently been suggested in the article titled “
DUAL DAMASCENE: OVERCOMING PROCESS ISSUES
” by Ruth DeJule in the June 2000 issue of
SEMICONDUCTOR INTERNATIONAL
to use a bilayer resist to form a dual inlaid via for a dual damascene process. An example of the “via first ” dual damascene process using a bilayer resist, similar to the one described in the DeJule article, is illustrated in
FIGS. 1A-F
.
FIG. 1A
illustrates a portion of an in process metallization section
1
of a semiconductor device. The metallization section contains a first conductive layer
3
and an insulating layer
5
formed over the first conductive layer
3
. The conductive layer
3
may be a metal interconnect, such as an aluminum interconnect. The insulating layer
5
contains a narrow via
7
which extends from the top surface
9
of the insulating layer
7
to the first conductive layer
3
. The via
7
has a circular cross section and contains only one sidewall
11
having a circular perimeter.
A conventional, bilayer resist film
12
, is formed in the via
7
and over the upper surface
9
of the insulating layer
5
, as shown in FIG.
1
B. The bilayer resist
12
includes a bottom antireflection coating (“BARC”)
13
and a top imaging layer
14
. The BARC
13
is typically a water soluble organic fluoropolymer which absorbs rather than reflects a majority of the exposing radiation. The top imaging layer
14
is a silicon containing polymer, such as a silane polymer, that is sensitive to selective radiation exposure. As shown in
FIG. 1B
, the bilayer resist
12
has a thickness of 2,500 to 3,500 angstroms. However, the BARC
13
is relatively thin and does not extend far above the upper surface
9
of the insulating layer. For example, the BARC
13
extends less than about 100 angstroms above the upper surface
9
of the insulating layer, creating a dip or recess
10
above the via
7
. A small portion of the imaging layer
14
is present in the recess
10
in the BARC
13
above the top portion of the via
7
.
The bilayer resist
12
is selectively exposed to radiation through a conventional lithographic mask or reticule (not shown), as illustrated in FIG.
1
C. During the exposure, a first portion
15
of the imaging layer
14
over the upper surface
9
of the insulating layer
5
directly adjacent to via
7
sidewall
11
and a second portion
17
of the imaging layer
14
above the via
7
are exposed, as indicated by the cross hatching in
FIG. 1C. A
third portion
19
of the imaging layer
14
over the upper surface
9
of the insulating layer
5
distal from the via sidewall
11
, is shielded by the mask and is not exposed to radiation. The exposed positive imaging layer
14
is then developed and patterned to remove the exposed first and second portions
15
,
17
while leaving the third portion
19
of the imaging layer
14
on the BARC
13
as a mask.
The exposed first portion
15
A of the BARC
13
above the upper surface of the insulating layer
5
and a second portion
17
A of the BARC
13
in the via
7
are removed by selective etching, such as by oxygen plasma etching, as illustrated in FIG.
1
D. The third portion
19
A of the BARC
13
that is masked by the third portion
19
of the imaging layer
14
is not removed because the imaging layer is not substantially removed by the oxygen plasma. The removal of the first and second portions
15
A,
17
A of the BARC
13
exposes a portion of upper surface
9
of the insulating layer
5
.
The exposed portion of the insulating layer
5
is etched using the third portion
19
/
19
A of the bilayer resist
12
as a mask to form a trench
21
having a width greater than that of the via
7
. The remaining third portion
19
/
19
A of the bilayer resist
12
is then removed by conventional methods, as illustrated in FIG.
1
E. The top of the via
7
is located in a bottom surface
23
of the trench
21
. In other words, the exposed portion of the insulating layer
5
is etched to remove a top section of the exposed portion of the insulating layer, without etching the bottom section of the exposed portion.
The dual damascene process is then completed by forming a second conductive layer
25
, as illustrated in FIG.
1
F. The second conductive layer
25
may be a metal layer which is formed in the trench
21
, such that it extends through the via
7
to contact the first conductive layer
3
. The second conductive layer is planarized by chemical mechanical polishing or etch back such that its top surface is even with the upper surface
9
of the insulating layer
5
.
However, the prior art dual damascene process suffers from a problem of via poisoning. This problem is illustrated in FIG.
2
. During the bilayer resist
12
exposure step illustrated in
FIG. 1C
, the second portion
17
A of the BARC
13
binds to the via
7
sidewall
11
and forms a rigid mushroom shape, as shown in FIG.
2
. The bound top section of the second portion
17
A is schematically illustrated by double cross hatches. Therefore, the second portion
17
A of the BARC
13
cannot be removed or fully removed from the via
7
during subsequent oxygen plasma etching step because it is chemically and/or physically bound to the via sidewall
11
. Thus, the second conductive layer
25
cannot contact or fully contact the first conductive layer
3
through the via
7
, because the via
7
is filled by the second portion
17
A of the BARC
13
which is rigidly bound to the via
7
sidewall
11
. This causes an open circuit between the first and second conductive layers or a poorly conductive path there between, which leads to device failure. This poison via problem is especially severe when the insulating layer
5
is a low-k (i.e., a low dielectric constant) polymer material, such as hydrogensilsesquioxane (HSQ).
BRIEF SUMMARY OF THE INVENTION
According to one aspect of the present invention, there is provided a method of making a dual inlaid via in a first layer, comprising forming a first opening in the first layer, forming a bilayer resist comprising an imaging layer above a BARC in the first opening, such that a lower section of the BARC is located in the first opening and an upper section of the BARC extends above the first opening, selectively exposing the imaging layer to radiation, patterning the bilayer resist, forming a second opening in communication with the first opening using the patterned bilayer resist as a mask, and wherein said bilayer resist forming step includes forming the BARC such that said upper section of the BARC extends above the first opening to a first height that is sufficient to substantially prevent exposing radiation from reaching a lower section of the BARC located in the first opening.
According to another aspect of the present invention, there is provided a method of making a semiconductor device containing a dual damascene contact, comprising forming a via in a polymer containing insulating layer, forming a bilayer resist comprising an imaging layer above a BARC in the via, such that a lower section of the BARC is located in said via and an upper section of the BARC extends above the via, selectively exposing the imaging layer to radiation and patterning the exposed imaging layer to remove a first portion of the imaging layer above the upper surface of the insulating layer adjacent to via sidewall and a second portion of the imaging layer over the via, while leaving a third portion of the imaging layer over the upper surface of the insulating layer distal from the via sidewall. The method further comprises removing a first portion of the BARC above the upper surface of the insulating layer adjacent to the via sidewall and a second portion of the BARC in the via

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