Semiconductor device manufacturing: process – Chemical etching – Vapor phase etching
Reexamination Certificate
2002-03-05
2004-03-30
Fahmy, Jr., Wael (Department: 2814)
Semiconductor device manufacturing: process
Chemical etching
Vapor phase etching
C216S047000
Reexamination Certificate
active
06713404
ABSTRACT:
TECHNICAL FIELD
The invention pertains to semiconductor constructions and methods of forming semiconductor constructions. In particular aspects, the invention pertains to semiconductor constructions in which an organic material is provided between photoresist and a layer comprising silicon and nitrogen, and to methods of forming such constructions.
BACKGROUND OF THE INVENTION
Photolithography is a commonly-used method for patterning features during semiconductor processing. A photosensitive material (photoresist) is formed over a mass which is ultimately to be patterned, and the photoresist is subsequently subjected to radiation. The radiation is provided in a pattern so that some portions of the photoresist are impacted by the radiation while other portions of the photoresist are not impacted by the radiation. The photoresist is then subjected to developing conditions which selectively remove either the impacted or non-impacted portions. If the photoresist is a positive photoresist, the impacted portions are selectively removed; and if the photoresist is a negative photoresist, the non-impacted portions are selectively removed.
The photoresist remaining after the development defines a patterned mask. The pattern of the mask can subsequently be transferred to the underlying mass utilizing appropriate etching conditions to form patterned features within the mass.
A difficulty which can be encountered during photolithographic processing is that the radiation utilized to pattern the photoresist (typically light) can be reflected from the underlying mass to cause various constructive and destructive interference patterns to occur in the light as it passes through the photoresist. This can adversely affect a pattern ultimately developed in the photoresist.
The problem is typically addressed by providing an antireflective coating immediately beneath the photoresist. Various antireflective coatings have been developed, with a deposited antireflective coating (DARC) being exemplary. Deposited antireflective coatings will typically comprise silicon and nitrogen, and can, for instance, consist of, or consist essentially of, silicon, nitrogen and optionally, hydrogen. DARC's can alternatively comprise silicon, oxygen, and in some cases, hydrogen, and can be referred to as silicon oxynitride materials.
DARC materials can be particularly useful as antireflective coatings during photolithographic processing of metals, and/or insulative materials (with an exemplary insulative material being borophosphosilicate glass).
An exemplary photolithographic fabrication process utilizing a DARC material is described with reference to
FIGS. 1 and 2
. Referring initially to
FIG. 1
, a fragment of a semiconductor construction
10
is illustrated at a preliminary processing stage. Construction
10
comprises a substrate
12
. Substrate
12
can include, for example, a semiconductive material (such as, for example, monocrystalline silicon). To aid in interpretation of the claims that follow, the terms “semiconductive substrate” and “semiconductor substrate” are defined to mean any construction comprising semiconductive material, including, but not limited to, bulk semiconductive materials such as a semiconductive wafer (either alone or in assemblies comprising other materials thereon), and semiconductive material layers (either alone or in assemblies comprising other materials). The term “substrate” refers to any supporting structure, including, but not limited to, the semiconductive substrates described above.
A mass
14
is supported by substrate
12
. Mass
14
can comprise an insulative material (such as, for example, borophosphosilicate glass) and/or various metals and/or metal compounds. Mass
14
is shown as a single uniform layer, but it is to be understood that mass
14
can comprise stacks of various materials.
An antireflective coating layer
16
is shown formed over mass
14
. Layer
16
will preferably comprise a DARC, such as, for example, silicon oxynitride.
A photoresist
18
is shown formed over and physically against antireflective coating
16
.
Radiation
20
is shown impacting various regions of photoresist
18
. Radiation
20
will typically comprise light, and can, for example, predominately comprise light having a wavelength which is in the region of from about 150 nanometers to about 250 nanometers. Regions of photoresist
18
impacted by radiation
20
are illustrated generally with the label
22
, and regions of the photoresist
18
which are not impacted by radiation
20
are illustrated generally with the label
24
.
Photoresist
18
can comprise a chemically amplified photoresist. In such application, radiation
20
will create a photogenerated catalyst (typically a strong acid) within regions
22
of the photoresist. The photoresist is then subjected to a post-exposure bake wherein the photogenerated catalyst causes further reactions to alter solubility of exposed regions
22
(and in some applications regions proximate exposed regions
22
) relative to regions
24
in a developer solution. An advantage of utilizing chemically amplified photoresists is that such can increase the sensitivity of photoresist to radiation by enabling a single incident photon to be responsible for many chemical events.
Photoresist
18
can be referred to as a photoresist system to indicate that the photoresist can comprise various components ultimately affected by exposure of a portion of photoresist
18
to light. For instance, if material
18
comprises a chemically amplified photoresist system, it will typically comprise a photoactive species which ultimately forms a photocatalyst (typically an acid) upon exposure to light having a suitable wavelength. The photoactive species then interacts with other materials present in the photoresist system to alter chemical properties of the system. The material
18
can be referred to as consisting essentially of a photoresist system to indicate that the material
18
consists essentially of components which are patterned during a photolithographic process to form a mask. Photoresist system
18
can, in particular applications, comprise a multilayer resist.
FIG. 2
illustrates construction
10
after a suitable post-exposure bake, and subsequent exposure to a developing solution. Photoresist
18
is illustrated as being a positive photoresist, and accordingly impacted regions
22
(
FIG. 1
) are selectively removed relative to non-impacted regions
24
.
A problem with utilization of DARC is that such can scavenge photogenerated catalysts (such as acid) during the post-exposure bake of photoresist
18
, and can accordingly interfere with the patterning of the photoresist. For instance, the patterned photoresist of
FIG. 2
is shown to comprise blocks
30
and
32
and such blocks are wider proximate antireflective coating
16
than at upper surfaces of the blocks. The widened regions at the blocks can be referred to as foot portions
34
. Such foot portions are undesired.
It would be desirable to develop photolithographic processing methods which alleviate or prevent formation of foot portions
34
.
SUMMARY OF THE INVENTION
In one aspect, the invention includes a semiconductor construction comprising a semiconductor substrate, and a first layer comprising silicon and nitrogen over the substrate. A second layer comprising at least 50 weight % carbon is over and physically against the first layer, and a third layer consisting essentially of a photoresist system is over and physically against the second layer.
In another aspect, the invention encompasses a method of forming a semiconductor construction. A semiconductor substrate is provided, and a first layer comprising silicon and nitrogen is formed over the substrate. A second layer comprising at least 50 weight % carbon is formed over the first layer, and a third layer consisting essentially of a photoresist system is formed over and physically against the second layer. A first portion of the third layer is exposed to radiation while a second portion of the third layer is not exposed to the radiatio
Fahmy Jr. Wael
Micro)n Technology, Inc.
Peralta Ginette
Wells St. John P.S.
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