Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2002-12-03
2004-10-05
Zarneke, David A. (Department: 2829)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S620000, C438S622000, C438S637000, C438S639000, C438S780000, C438S949000
Reexamination Certificate
active
06800551
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a chemical amplification (or chemically amplified) type [Kagakuzofuku-gata] photoresist composition, a method for producing a semiconductor device using the composition, and a semiconductor substrate. More particularly, it relates to a chemical amplification type photoresist composition for prohibiting resist pattern resolution defects, a method for producing a semiconductor device using the composition, and a semiconductor substrate.
Definition: The term “chemical amplification (or chemically amplified) type photoresist” used herein denotes a class of the photoresist that falls within the following category:
Chemical amplification type photoresist composition means a composition containing an acid generating agent as a sensitizer in the resist, generating acid therefrom upon light exposure, thus inducing the catalytic reaction by the generated acid during the subsequent heat treatment, thereby accelerating soluble or insoluble property against the developing solution.
BACKGROUND OF THE INVENTION
As a method for forming multi-layered wirings for a semiconductor integrated circuit, buried wirings (Damascene techniques) is effective. In these techniques, the dual Damascene technique, consisting in forming a wiring trench for forming an upper layer wiring and a via hole or a contact hole interconnecting the upper layer wiring and a lower layer wiring or substrate in an insulating film, and in burying the same metal film in both the wiring trench and the via hole to form the interconnections and the via as one, gives rise to an advantage that production costs may be lowered appreciably through simplifying and expediting the production process.
On the other hand, a low dielectric constant film (Low-k film) has been brought into use as an inter-layer insulating film intermediate the wirings in the multilayer wiring structure, in order to diminish the capacitance across neighboring wirings to reduce signal delay through the wirings.
An instance of a conventional via first dual Damascene interconnection forming method is now explained.
First, a first etching barrier film
7
, a first inter-layer insulating film
6
, a second etching barrier film
5
, a second inter-layer insulating film (low dielectric constant film)
4
, and a cap film (insulating film)
3
, are formed on an underlying Cu wiring layer
8
, in this order, looking from the substrate side. An anti-reflection film then is coated on the entire substrate surface, and a first photoresist pattern for forming via-holes is deposited on the surface of the anti-reflection film. Using this first photoresist pattern as an etching mask, the anti-reflection film, cap film
3
, second inter-layer insulating film
4
, second etching barrier film
5
and the first inter-layer insulating film
6
are selectively continuously etched, until the first etching barrier film
7
is exposed. This forms a via-hole
21
(see
FIG. 9
a
).
The anti-reflection film and the first photoresist pattern are then removed by ashing or an organic removing (peeling) liquid (see
FIG. 9
a
). An anti-reflection film
2
then is formed on the entire substrate surface such that the via-hole
21
is not completely buried (see
FIG. 9
b
). A photoresist
1
then is coated on the surface of the anti-reflection film
2
(see
FIG. 9
c
). The coated photoresist is exposed to light to form a second photoresist pattern
1
for forming a wiring trench (see
FIG. 9
d
). Using this second photoresist pattern as an etching mask, the anti-reflection film
2
, cap film
3
and the second inter-layer insulating film
4
are selectively continuously etched until the second etching barrier film
5
is exposed (see
FIGS. 9
e
and
f
). This forms a wiring trench
22
.
The anti-reflection film
2
and the second photoresist pattern
1
are then peeled or removed by ashing or with an organic removing solution. The exposed first etching barrier film
7
then is etched by an etchback method until the underlying Cu wiring layer
8
is exposed (see
FIG. 9
g
). The substrate, the underlying Cu wiring layer
8
of which has now been exposed, is rinsed. After forming a seed film and a metal barrier film on the substrate, a Cu plating film
9
is deposited until it is buried in the via-hole and in the wiring trench. The Cu plating film
9
and the cap film
3
are planarized by CMP (chemical mechanical polishing) until the cap film
3
is substantially ground off by polishing (see
FIG. 9
h
). This forms a dual Damascene wiring
9
electrically connected to the lower Cu wiring layer
8
(See JP-P2001-217242A).
SUMMARY OF THE DISCLOSURE
According to an experiment, conducted by the present inventors, if, with use of a conventional chemical amplification type photoresist composition (positive type) as the photoresist, the second photoresist pattern
1
is formed, the photoresist in the via-hole
21
and in the neighboring area is not decomposed, even on light exposure, such that the photoresist is left over even on processing with the developing solution (see
FIG. 9
d
. The state of the substrate surface is shown in
FIG. 3
as Comparative Example. Referring to respective patterns in the Comparative Example, the portions of the substrate, corresponding to the via-holes, are inherently represented in black as a shadow of the groove. In the present Comparative Example, there are those via-holes in which the black shadows by the groove are not represented such that the via-holes are charged with the photoresist buried therein.
According to the technical information, acquired by the present inventors, the reason this problem arises is that, if the anti-reflection film and the chemical amplification type photoresist composition are coated and exposed to light without pre-treatment (such as heating, UV processing or oxygen plasma processing), the pollutants, such as basic compounds or moisture, affixed to or soaked into the substrate surface (such as via-hole wall surface of the inter-layer insulating film), tend to be transmitted through the anti-reflection film at the time of baking the anti-reflection film and the photoresist (pre-baking for solvent removal) so as to be intruded into the photoresist.
That is, in the via first dual Damascene method, an organic alkaline removing solution is used to remove the resist pattern used for forming the via-hole. The pollutants contained in this organic removing solution, such as basic compounds (amino components), moisture in air or floating basic compounds, are affixed to or seep into the via-hole wall surface (inter-layer insulating film) where the pollutants are concentrated. If the anti-reflection film for the wiring groove and the photoresist (chemical amplification type positive photoresist composition) are then coated on the substrate surface, inclusive of the via-hole wall surface, and pre-baked, the pollutants concentrated on the via-hole wall surface are transmitted from the via-hole wall surface through the anti-reflection film so as to be intruded into the photoresist. The so intruded pollutants, such as amino compounds, are neutralized with catalytic acids (H
+
) yielded on light exposure due to photodecomposition of the acid generating agents contained in the photoresist (chemical amplification type positive photoresist composition). Should this neutralization reaction between the pollutants and the acid catalyst occur, the acid catalyst in the photoresist is deactivated and hence falls into shortage. This phenomenon is known as poisoning. The photoresist lying in an area where the acid catalyst is deactivated cannot be turned, even on light exposure, into a substance soluble in a developing solution (change in polarity). For example, protective groups, such as acetyl groups, cease to exhibit protective action such that the chain reaction into hydroxyl groups is scarcely produced. The area of the substrate which has not been turned into the developing solution, such as the inside of the via-hole or its vicinity, is left over without being dissolved in the developing soluti
Nagahara Seiji
Sakurada Toyohisa
Yoshihara Takao
NEC Electronics Corporation
Sarkar Asok Kumar
Zarneke David A.
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