Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Radiation mask
Reexamination Certificate
2000-06-01
2002-07-23
Rosasco, S. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Radiation mask
Reexamination Certificate
active
06423455
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to methods for fabricating photomasks which in turn are employed for fabricating microelectronic fabrications. More particularly, the present invention relates to methods for fabricating multiple masking layer photomasks which in turn are employed for fabricating microelectronic fabrications.
2. Description of the Related Art
Microelectronic fabrications are formed from microelectronic substrates over which are formed patterned microelectronic conductor layers which are separated by microelectronic dielectric layers. Common in the art of microelectronic fabrication for use when fabricating microelectronic fabrications is the use of photolithographic methods which in turn employ photomasks for defining dimensions of patterned photoresist layers which further in turn are employed for defining dimensions of microelectronic devices and patterned microelectronic layers within microelectronic fabrications.
As microelectronic fabrication integration levels have increased and microelectronic device and patterned microelectronic conductor layer dimensions have decreased, it has become common in the art of microelectronic fabrication when employing photolithographic methods which employ photomasks for defining dimensions of patterned photoresist layers which further in turn are employed for defining dimensions of microelectronic devices and patterned microelectronic layers within microelectronic fabrications to employ photomask constructions which provide for enhanced intensity resolution of a photoexposure radiation beam which is employed for photoexposing a blanket photoresist layer when forming a patterned photoresist layer. As is understood by a person skilled in the art, a class of photomask constructions which provides for such an enhanced intensity resolution of a photoexposure radiation beam employed for photoexposing a blanket photoresist layer when forming a patterned photoresist layer is the phase shift mask (PSM) class of photomask constructions.
While there exists within the art of microelectronic fabrication various types of phase shift mask (PSM) photomask constructions which effectively provide for enhanced intensity resolution of a photoexposure radiation beam passed through a phase shift mask (PSM) photomask construction for use when forming a patterned photoresist layer from a blanket photoresist layer, from a practical perspective of ease of fabrication, a particularly desirable phase shift mask (PSM) photomask construction is an attenuated phase shift mask (APSM) photomask construction. A schematic cross-sectional diagram of an attenuated phase shift mask (APSM) photomask construction is illustrated within the schematic cross-sectional diagram of FIG.
1
.
As is illustrated within the schematic cross-sectional diagram of
FIG. 1
, there is shown an attenuated phase shift mask (APSM) photomask construction
14
comprising a transparent substrate
10
having formed thereupon a series of patterned semi-transparent masking layers
12
a
,
12
b
and
12
c
. Within the attenuated phase shift mask (APSM) photomask construction
14
whose schematic cross-sectional diagram is illustrated in
FIG. 1
, the series of patterned semi-transparent masking layers
12
a
,
12
b
and
12
c
is formed of a semi-transparent masking material, typically and preferably having a transmissivity of from about 3 to about 8 percent of an incident photoexposure radiation beam
16
incident upon the attenuated phase shift mask (APSM) photomask construction
14
. As is further illustrated within the schematic cross-sectional diagram of
FIG. 1
, the incident photoexposure radiation beam
16
comprises: (1) a first incident photoexposure radiation beam
16
a
which passes through only the transparent substrate
10
; and (2) a second incident photoexposure radiation beam
16
b
which passes through both the transparent substrate
10
and the patterned semi-transparent masking layer
12
c
. As is finally illustrated within the schematic cross-sectional diagram of
FIG. 1
, the patterned semi-transparent masking layer
12
c
is formed of a composition, and in particular of a thickness, such that subsequent to passing through the attenuated phase shift mask (APSM) photomask construction
14
whose schematic cross-sectional diagram is illustrated in
FIG. 1
the first incident photoexposure radiation beam
16
a
and the second incident photoexposure radiation beam
16
b
are 180 degrees out of phase, which in turn provides the enhanced intensity resolution of the photoexposure radiation beam
16
once passed through the attenuated phase shift mask (APSM) photomask construction
14
whose schematic cross-sectional diagram is illustrated in FIG.
1
.
While attenuated phase shift mask (APSM) photomask constructions are thus desirable within the art of microelectronic fabrication for ultimately providing within the art of microelectronic fabrication microelectronic devices and patterned microelectronic layers with enhanced resolution, phase shift mask (PSM) photomask constructions in general, and attenuated phase shift mask (APSM) photomask constructions in particular, are not entirely without problems in the art of microelectronic fabrication. In that regard and in particular with respect to attenuated phase shift mask (APSM) photomask constructions, while attenuated phase shift mask (APSM) photomask constructions do in fact provide a comparatively simple phase shift mask (PSM) photomask construction in comparison with other types of phase shift mask (PSM) photomask constructions, by the nature of their construction which includes a series of patterned semi-transparent layers, attenuated phase shift mask (APSM) photomask constructions also suffer from enhanced photoexposure radiation leakage in locations where such photoexposure radiation leakage might otherwise be undesirable.
It is thus in general towards the goal of providing, for use when fabricating microelectronic fabrications, photomask constructions, such as but not limited to attenuated phase shift mask (APSM) photomask constructions, with enhanced properties, that the present invention is directed.
Various methods for fabricating photomask constructions, and the photomask constructions resulting from the methods, have been disclosed in the art of microelectronic fabrication for providing photomask constructions with desirable properties for use to within the art of microelectronic fabrication.
For example, Garza, in U.S. Pat. No. 5,716,738, discloses an attenuated phase shift mask (APSM) photomask construction having an opaque border layer which attenuates spurious photoexposure of a photoresist layer which is photoexposed while employing the attenuated phase shift mask (APSM) photomask construction. To realize the foregoing object, the opaque border layer within the attenuated phase shift mask (APSM) photomask construction is formed employing an opaque photosensitive material, such as an opaque photosensitive polyimide material.
In addition, Tzu et al., in U.S. Pat. No. 5,783,337, discloses a method for fabricating an attenuated phase shift mask (APSM) photomask construction which similarly also employs an opaque border layer which attenuates spurious photoexposure of a photoresist layer which is photoexposed while employing the attenuated phase shift mask (APSM) photomask construction. To realize the foregoing object, the method employs when fabricating the attenuated phase shift mask (APSM) photomask construction a single blanket photoresist layer which is sequentially photoexposed twice with varying intensity of a focused electron beam radiation source such that incident to further processing of the twice photoexposed blanket photoresist layer there may be formed from a blanket chromium layer formed beneath the blanket photoresist layer a patterned chromium layer for use on the opaque border layer surrounding an active region of the attenuated phase shift mask (APSM) photomask construction.
Further, Chen, in U.S. Pat. No. 5,789,117, also discloses a
Rosasco S.
Taiwan Semiconductor Manufacturing Company , Ltd.
Tung & Associates
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