Semiconductor device manufacturing: process – Chemical etching – Combined with coating step
Reexamination Certificate
2003-06-03
2004-12-07
Fourson, George (Department: 2823)
Semiconductor device manufacturing: process
Chemical etching
Combined with coating step
C438S233000, C438S624000, C438S675000, C438S734000, C438S702000, C438S703000
Reexamination Certificate
active
06828238
ABSTRACT:
TECHNICAL FIELD
The invention pertains to methods of forming openings through electrically insulative caps to electrically conductive materials.
BACKGROUND OF THE INVENTION
Various semiconductor constructions comprise an insulative cap stacked over a conductive material. For instance, wordlines and bitlines typically comprise conductive materials patterned as lines extending across a semiconductor substrate, and protected by electrically insulative caps formed over the electrically conductive lines.
It is frequently desired to form openings extending through the protective cap to the conductive material beneath the cap. For instance, it can be desired to form an electrical interconnect extending to the electrically conductive material of a wordline or bitline. This is commonly accomplished by forming an opening extending through an electrically insulative protective cap to expose electrically conductive material of the wordline or bitline, and subsequently filling the opening with an electrically conductive material to form the electrical interconnect to the conductive material of the wordline or bitline.
A prior art process for forming an electrical interconnect to conductive material of a line is described with reference to
FIGS. 1 and 2
. Referring initially to
FIG. 1
, a semiconductor construction
10
includes a substrate
12
having an upper surface
14
. Substrate
12
can comprise, for example, monocrystalline silicon lightly-doped with background p-type dopant. 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 thin layer of electrically insulative material
16
is formed over upper surface
14
, and an electrically conductive line
18
is formed over insulative material
16
. Insulative material
16
can comprise, for example, silicon dioxide. The electrically conductive material of line
18
can comprise, for example, one or more materials selected from the group of metals, metal compounds and conductively-doped silicon. Although line
18
is shown having a homogeneous cross section, it is to be understood that the line can comprise a stack of one or more electrically conductive layers of differing composition relative to one another. Line
18
would have a length extending into and out of the page relative to the
FIG. 1
cross-sectional view.
A protective material
20
is formed around electrically conductive line
18
. Protective material
20
is typically an electrically insulative material, and can comprise, consist essentially of, or consist of silicon nitride. A stack
22
can be considered to comprise protective material
20
, line
18
and insulative material
16
. The protective material
20
can extend around three sides of conductive material
18
in the stack (as shown), or, in other aspects (not shown) can be only over the top of material
18
.
A thick mass of electrically insulative material
24
is formed over stack
22
, as well as over surface
14
of substrate
12
. Mass
24
can comprise, for example, a silicate glass (such as, for example, borophosphosilicate glass (BPSG)). Mass
24
can be homogeneous, or can comprise a stack of electrically insulative materials. Mass
24
will typically comprise a thickness over stack
22
of at least about 10,000 Å, frequently at least about 15,000 Å, and even at least about 20,000 Å.
A patterned masking material
26
is formed over mass
24
. Masking material
26
can comprise, for example, photoresist, and can be patterned utilizing photolithographic processing. Patterned masking material
26
defines an opening
28
extending through the patterned masking material and to an upper surface of mass
24
.
Referring to
FIG. 2
, opening
28
is extended through mass
24
, through protective material
20
, and to an upper surface of conductive material
18
, utilizing a suitable etch. If mass
24
consists of a silicate glass, and protective material
20
consists of silicon nitride, a suitable etch for forming opening
28
can be an etch utilizing CF
4
.
A problem which occurs during formation of opening
28
is that even though etches are known which can etch both a silicate glass of mass
24
and a silicon nitride material of protective layer
20
, the etches will frequently be slower relative to a silicon nitride material than to a silicate glass. Accordingly, the downward progression of the etch slows once the etch reaches protective material
20
. The etch can then start to extend laterally outward which forms a widened region
30
of opening
28
.
A continuing goal of semiconductor processing is to reduce dimensions associated with circuit components to enable an increase in packing density of the components. Ultimately, a conductive interconnect is to be formed in opening
28
, and the widening of opening
28
confers an increased lateral dimension to the electrical interconnect. Such increased lateral dimension reduces a packing density that can be achieved. Accordingly, it is desired to develop new methods for forming openings which alleviate or prevent the widening associated with prior art processes.
SUMMARY OF THE INVENTION
The invention includes a method of forming an opening extending through an electrically insulative cap to an electrically conductive material. A substrate is provided. The substrate supports a stack and an electrical node. The stack includes an electrically insulative cap over an electrically conductive material. An electrically insulative layer is formed over the stack and over the electrical node. A first etch is utilized to etch through the electrically insulative layer to the electrical node and to the insulative cap. The first etch etches partially into the electrically insulative cap but does not etch entirely through the electrically insulative cap. A second etch is conducted after the first etch, and is utilized to etch entirely through the electrically insulative cap to the conductive material of the stack.
In another aspect, the invention includes a method of forming an opening through a silicon nitride-containing cap to an electrically conductive material. A substrate is provided, and the substrate supports a wordline stack and an electrical node. The stack comprises a silicon nitride-containing cap over an electrically conductive material. A first electrically insulative layer is formed over the stack and over the electrical node. A first etch is utilized to etch through the first electrically insulative layer to the electrical node and to the silicon nitride-containing cap. The first etch also etches partially into the silicon-nitride-containing cap, but does not etch entirely through the cap. The partial etching of the first etch into the silicon nitride-containing cap forms a first opening extending into the cap to a first depth. A second electrically insulative layer is formed within the first opening in the cap. The second electrically insulative layer is anisotropically etched to form, in at least one cross-sectional view, separated spacers within the first opening in the silicon nitride-containing cap. An electrically insulative material is formed over the stack, within the first opening, and over the separated spacers. The electrically insulative material has a total thickness of at least about 10,000 Å. A second etch is utilized to form a second opening which extends through the electrically insulative material, between the separated spacers, through the silicon nitride-containing cap, and to the electrically conductive material of the stack.
REFERENCES:
patent: 5362666 (1994-11-01), Dennison
patent: 5498570
Fourson George
Maldonado Julio J.
Wells St. John P.S.
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