Method for mitigating formation of silicon grass

Details Method for mitigating formation of silicon grass Method for mitigating formation of silicon grass

1999-10-21

2002-10-15

Baxter, Janet (Department: 1752)

Radiation imagery chemistry: process, composition, or product th

Imaging affecting physical property of radiation sensitive...

Making electrical device

C430S314000, C430S315000, C430S317000, C430S318000, C430S322000, C430S329000, C216S038000, C216S087000

Reexamination Certificate

active

06465156

ABSTRACT:

TECHNICAL FIELD
The present invention generally relates to a method for mitigating formation of silicon grass.
BACKGROUND OF THE INVENTION
In the semiconductor industry, there is a continuing trend toward higher device densities. Fabrication of very large scale integrated circuits (VLSI) and ultra large scale integrated circuits (ULSI) requires that resist materials, lithographic processes, and exposure tools meet necessary performance demands for high throughput manufacturing of sub-micron feature size devices. In the instance of sub-micron lithography, top surface imaging (TSI) is employed to increase resolution capability of optical exposure systems. Several TSI processes have been developed such as Diffusion Enhanced Silylated Resist (DESIRE) negative tone process and positive tone Silylated Acid Hardened Resist (SAHR).
Top surface imaging in general uses reactive ion etching (RIE) to dry develop patterns after exposure and silylation of a photoresist layer. A dry development process for top surface imaging requires high selectivity between exposed and unexposed regions of the photoresist to maintain critical dimensions, high anisotropy to provide vertical profiles in the patterned photoresist and also result in no residue after etching.
A significant problem with TSI resist processes is that RIE residue, in the form of “grass”, is produced. RIE grass is a problem in both positive and negative working systems, since residue free images are desired. The grass is produced as a result of silicon being incorporated into regions to be etched, such that micromasks are formed in those regions, thus preventing the desired regions from being completely etched during etching, resulting in the “grass”-like residue. Such residues are undesirable—for example, they may interfere with substrate metal and/or metal-to-metal contacts in subsequent metallization steps resulting in multitude of problems including contact resistance and metal adhesion.
Prior Art
FIGS. 1
a
-
1
e
describe a conventional silylation process on a structure
10
which results in the formation of grass. In
FIG. 1
a
, a substrate
16
has a metal layer
18
formed thereon, and a photoresist layer
20
lies over the metal layer
18
. The photoresist layer
20
is patterned and exposed to silicon containing vapor
24
as shown in
FIG. 1
b
. The exposed areas
26
of the photoresist layer
20
in
FIG. 1
c
have silicon formed thereon which will be subsequently (after being converted to SiO
2
) used as an etch mask during a metal layer etch. However, unexposed areas
28
of the photoresist layer
20
have trace amounts of silicon thereon. In
FIG. 1
d
, the structure
10
undergoes an O
2
plasma etch
40
to etch away desired portions of the photoresist layer. However, spikes
44
of photoresist can result (corresponding to the trace amounts of silicon residues on the photoresist layer
20
) as shown in
FIG. 1
e
. The spikes
44
will create problems in the subsequent metal layer etch.
In view of the above, it would be desirable for a method to eliminate or mitigate the formation of silicon “grass” residue formed from a silylation process.
SUMMARY OF THE INVENTION
The present invention provides for a method which mitigates formation of silicon grass. A silylation process is performed to render a portion of a photoresist mask O
2
resistant by treatment with an organo-silicon reagent in solution or in vapor phase after resist patterning. A chemical mechanical polishing (CMP) process is performed to remove any trace amounts of silicon that may have formed on unexposed areas of the photoresist layer as a result of the silylation process. After the CMP process is complete, the photoresist layer is plasma etched and then employed as an etch mask for the underlying layer (e.g., polysilicon layer, metal layer, silicon nitride layer, or oxide layer). The removal of trace amounts of silicon from the photoresist layer via the CMP process mitigates the formation of silicon grass. One aspect of the invention relates to a method for mitigating formation of silicon grass. A silylation process is performed on a semiconductor structure, the structure including a photoresist layer, an underlayer under the photoresist layer, and a substrate under the underlayer. A chemical mechanical polishing process is employed to remove a portion of the photoresist layer.
Another aspect of the invention relates to a method for mitigating formation of silicon grass. A silylation process is performed on a semiconductor structure, the structure including a photoresist layer, an underlayer under the photoresist layer, and a substrate under the underlayer. A chemical mechanical polishing process is employed to remove a portion of the photoresist layer. A reactive ion etch is performed to remove select portions of the photoresist layer, and an underlayer etch is performed to remove select portions of the underlayer.
Yet another aspect of the present invention relates to a method for mitigating formation of silicon grass. A silylation process is performed on a semiconductor structure, the structure including a photoresist layer having portions including trace amounts of silicon; and a chemical mechanical polishing process is performed to remove the trace amounts of silicon.
To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.


REFERENCES:
patent: 4978594 (1990-12-01), Bruce et al.
patent: 5259888 (1993-11-01), McCoy et al.
patent: 5312717 (1994-05-01), Sachdev et al.
patent: 5525192 (1996-06-01), Lee et al.
patent: 6277015 (2001-08-01), Robinson et al.

Affiliated with

Also associated with

Rating

Method for mitigating formation of silicon grass does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Method for mitigating formation of silicon grass, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for mitigating formation of silicon grass will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2987914