Semiconductor device manufacturing: process – Chemical etching – Liquid phase etching
Reexamination Certificate
2000-12-28
2003-05-13
Kunemund, Robert (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Liquid phase etching
C438S753000, C438S754000, C438S757000, C252S079100, C252S079200, C252S079300
Reexamination Certificate
active
06562727
ABSTRACT:
CLAIM FOR PRIORITY AND CROSS-REFERENCE TO OTHER APPLICATIONS
This application claims priority to Korean Application No. 00-41427, filed Jul. 19, 2000, the disclosure of which is hereby incorporated herein by reference.
FIELD OF THE INVENTION
The present invention relates to the field of integrated circuit fabrication in general and, more particularly, to the removal of anti-reflective layers during integrated circuit fabrication.
BACKGROUND OF THE INVENTION
As the density of integrated circuits increase, so may the need for forming fine patterns therein. For example, integrated circuit memory devices with a capacity of 1-Gigabit or more may need a pattern size having a design rule of about 0.2 &mgr;m or less. However, it may be difficult to use conventional i-line photoresists to form such fine patterns. Thus, a photolithography technique using Deep Ultraviolet (DUV) photoresist has been suggested.
It is known to deposit a photoresist layer on multiple material layers of an integrated circuit device and expose a portion of the photoresist layer to light develop the photoresist layer into photoresist patterns. An anti-reflective layer may be formed under the photoresist layer to prevent diffusion reflection from the underlying layers during exposure and thereby achieve higher resolution photolithography.
In particular, it is known to use a silicon oxynitride layer as the anti-reflective layer with a DUV photoresist. The silicon oxynitride layer can suppress diffusion reflection from the underlying layers. Furthermore, the silicon oxynitride layer may reduce undesirable effects that may occur during patterning of the photoresist layer. For example, the silicon oxynitride layer may help avoid a phenomenon referred to as photoresist poisoning, which can lead to a footing phenomenon after development of the photoresist layer.
FIGS. 1A through 1D
are cross-sectional views that illustrate a conventional method for fabricating integrated circuits. In particular,
FIGS. 1A through 1D
illustrate a photolithography process in which a silicon oxynitride layer can be used as an anti-reflective film in forming a gate electrode of a transistor.
First, according to
FIG. 1A
, a doped polysilicon layer and an anti-reflective layer, such as a silicon oxynitride layer, are sequentially deposited on an integrated circuit substrate
10
having an isolation region
12
and an oxide layer. After forming a photoresist pattern
28
on the resultant structure, the anti-reflective layer, the doped polysilicon layer and the oxide layer are sequentially etched using the photoresist pattern
28
as an etching mask, thereby resulting in an anti-reflective pattern
26
, a gate electrode
24
and a gate oxide layer
22
as shown in FIG.
1
A.
Next, the photoresist pattern
28
is removed to expose the anti-reflective pattern
26
on the gate electrode
14
, as shown in FIG.
1
B. The exposed anti-reflective pattern
26
can have a thickness of about 300 to 400 Angstroms. According to some conventional techniques, the anti-reflective pattern
26
can be removed during a cleaning process that uses a mixture of NH
4
OH, H
2
O
2
and deionized water in a ratio of 1:4:20 by volume (hereinafter, referred to as “SC-1”) as the cleaning solution. In other conventional processes an HF solution can be used as the cleaning solution. The cleaning process can be followed by a rinsing process using deionized water.
Unfortunately, when SC-1 is used to etch the anti-reflective pattern
26
, the underlying polysilicon layer of the gate electrode
24
may also be etched. On the other hand, if an HF solution is used to remove the anti-reflective pattern
26
, the anti-reflective pattern
26
may not be fully removed, such that a remnant anti-reflective pattern
26
a
may remain on the gate electrode
24
. Moreover, the remnant anti-reflective pattern
26
a
may include semi-spherical defects (or seeds).
The defects can be caused by the porous nature of the silicon oxynitride layer. In particular, when an unstable porous structure, such as the silicon oxynitride layer, is present on a hydrophobic layer, such as the polysilicon layer, a portion of the unstable porous structure (i.e., the silicon oxynitride layer) may remain on the surface of hydrophobic layer (i.e., the polysilicon layer) after cleaning. Seeds may have an increased tendency to form on a hydrophobic layer compared to a hydrophilic layer, due to the presence of dangling bonds on its surface.
The remaining portion of the silicon oxynitride layer may react with silica (Si
x
O
y
) in the deionized water that is used in the rinsing process to cause the semi-spherical defects. The remnant anti-reflective pattern
26
a
may act as a barrier in subsequent ion implantation or metal silicide formation, thereby increasing the probability of a device failure.
The remnant anti-reflective pattern
26
a
, including the semi-spherical defects which remains on the gate electrode
24
, may be removed by increasing the amount of etching during the a chemical cleaning process. However, as shown in
FIG. 1D
, the isolation region
12
may be unacceptably recessed or an undercut
22
a
may be formed in the gate oxide layer
22
by increased etching. Thus, it can be difficult to provide processing margins sufficient to remove the anti-reflective pattern
26
while reducing over etching of other portions of the integrated circuit.
SUMMARY OF THE INVENTION
Embodiments according to the present invention can provide methods and compositions for the removal of anti-reflective layers during fabrication of integrated circuits. Pursuant to these embodiments, an anti-reflective pattern or layer can be removed from an integrated circuit using a solution that includes a fluorine containing compound, an oxidant, and water. In some embodiments, the fluorine containing compound in the solution is Hydrogen Fluoride (HF). Preferably, the oxidant in the solution is H
2
O
2
. In some embodiments, the oxidant in the solution is ozone water. The water can be deionized water.
In some embodiments according to the present invention, the solution can be about 50% or more oxidant by volume. In some embodiments according to the present invention, a ratio of the fluorine containing compound to the oxidant in the solution can be in a range between about 14:800 and 14:1000 by volume. In some embodiments according to the present invention, the fluorine containing compound can be an HF solution that is 49% pure.
In other embodiments according to the present invention, the oxidant can be 30% pure H
2
O
2
that is in a range between about 50% and 80% of the solution by volume. In other embodiments according to the present invention, a ratio of the fluorine containing compound to the oxidant to the deionized water in the solution can be in a range between about 14:1100:300 to 14:1000:400 by volume.
In other embodiments according to the present invention, an integrated circuit can be fabricated by forming a conductive layer on an integrated circuit substrate. An anti-reflective layer can be formed on the conductive layer. A photoresist pattern can be formed on the anti-reflective layer. The anti-reflective layer and the conductive layer can be etched using the photoresist pattern as an etching mask to provide an anti-reflective pattern and a gate electrode. The anti-reflective pattern can be removed using a solution containing a fluorine containing compound and an oxidant.
In some embodiments according to the present invention, an anti-reflective layer removal composition can include a solution of a fluorine containing compound, an oxidant, and water. The solution can about 50% or more oxidant by volume. In some embodiments according to the present invention, a ratio of the fluorine containing compound to the oxidant in the solution can be in a range between about 14:800 and 14:1000 by volume. In other embodiments, the solution can be less than about 80% oxidant by volume. In some embodiments according to the present invention, the water can be deionized water.
In some embodiments according to the present invention, th
Yeo In-jun
Yoon Byoung-moon
Brown Charlotte A.
Kunemund Robert
Myers Bigel Sibley & Sajovec P.A.
Samsung Electronics Co,. Ltd.
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