Coating apparatus – Condition responsive control
Reexamination Certificate
2000-03-08
2003-03-18
Chaudhuri, Olik (Department: 2823)
Coating apparatus
Condition responsive control
Reexamination Certificate
active
06533865
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to lithography and more particularly relates to a system and method for reducing microbubbles in a developer solution.
BACKGROUND OF THE INVENTION
Lithography in semiconductor processing relates generally to the process of transferring patterns which correspond to desired circuit components onto one or more thin films which overlie a substrate. One important step within the field of lithography involves optical tools and methods for transferring the patterns to the films which overlie the semiconductor wafer. Patterns are transferred to a film by imaging various circuit patterns onto a photoresist layer which overlies the film on the wafer. This imaging process is often referred to as “exposing” the photoresist layer. The benefit of the exposure process and subsequent processing allows for the generation of the desired patterns onto the film on the semiconductor wafer, as illustrated in prior art
FIGS. 1
a
-
1
f.
Prior art
FIG. 1
a
illustrates a photoresist layer
10
deposited by, for example, spin-coating, on a thin film
11
such as, for example, silicon dioxide (SiO
2
) which overlies a substrate
12
such as silicon. The photoresist layer
10
is then selectively exposed to radiation
13
(e.g., ultraviolet (UV) light) via a photomask
14
(hereinafter referred to as a “mask”) to generate one or more exposed regions
16
in the photoresist layer
10
, as illustrated in prior art
FIG. 1
b.
Depending on the type of photoresist material utilized for the photoresist layer
10
, the exposed regions
16
become soluble or insoluble in a specific solvent which is subsequently applied across the wafer (this solvent is often referred to as a developer).
The exposed regions
16
are made either soluble or insoluble in the developer. When the exposed regions
16
are made soluble, a positive image of the mask
14
is produced in the photoresist layer
10
, as illustrated in prior art
FIG. 1
c,
and the photoresist material is therefore referred to as a “positive photoresist”. The exposed underlying areas
18
in the film
11
may then be subjected to further processing (e.g., etching) to thereby transfer the desired pattern from the mask
14
to the film
11
, as illustrated in prior art
FIG. 1
d
(wherein the photoresist layer
10
has been removed). Conversely, when the exposed regions
16
are mode insoluble, a negative image of the mask
14
is produced in the photoresist
10
layer, as illustrated in prior art
FIG. 1
e,
and the photoresist material is therefore referred to as a “negative photoresist”. In a similar manner, the exposed underlying areas
20
in the film
11
may then be subjected to further processing (e.g., etching) to thereby transfer the desired pattern from the mask
14
to the film
11
, as illustrated in prior art
FIG. 1
f.
The photoresist is formed typically on the wafer using a process called spin coating. Similarly, the developer material is also spin coated onto the wafer by applying developer material across the photoresist and then spin coating the developer material until centrifugal forces disperse the developer material over the coating of resist. A prior art developer nozzle system is illustrated in prior art
FIG. 2. A
developer nozzle
40
applies a developer solution or material
46
on a photoresist layer
48
disposed on a wafer
50
. The wafer
50
is vacuum held onto a rotating chuck
52
driven by a shaft
54
which is coupled to a motor
56
. The developer material
46
flows outward from the center of the photoresist material layer
48
covering the entire top surface thereof.
Due to the surface of the photoresist material layer on the semiconductor being highly hydrophobic, the photoresist surface can repel the developer material at the initial state of jetting out the developer material from the developer supply nozzle so that turbulent flow of the developer material is generated on the surface of the photoresist, resulting in the formation of microbubbles at the photoresist/developer interface, as illustrated in prior art FIG.
3
. The microbubbles produced between the photoresist material layer and the developer material are a cause of defects in the resulting photoresist pattern.
A conventional solution to this problem has been to apply a washing solution material or liquid (e.g., water), that is typically used in a rinsing or washing process, onto the photoresist material layer and spin coat the washing solution material to form a washing solution material film. The developer material is then applied to the wafer and the spin coated thereon, and the washing solution material film is scattered off the surface of the photoresist material layer leaving only the developer material. Although the wetting step helps reduce the number of microbubbles at the photoresist/developer interface, it does not eliminate the problem. Consequently, as feature sizes continue to shrink, resist defects will to continue to adversely impact lithography performance.
SUMMARY OF THE INVENTION
The present invention relates to a system and method of improving lithography performance by eliminating microbubbles associated with a developer solution.
According to one aspect of the present invention, a system and method of eliminating microbubbles in a developer solution is disclosed. Microbubbles associated with the developer solution are eliminated by agitating the developer solution which overlies the exposed photoresist with waves, such as acoustic waves or ultrasonic waves. The waves break the microbubbles from the photoresist/developer interface and cause the microbubbles to move through and exit from a surface of the developer. Elimination of the microbubbles results in reduced defects in the resulting patterned photoresist, thereby improving subsequent patterning utilizing the patterned photoresist.
According to another aspect of the present invention, a system and method of eliminating microbubbles includes one or more sensors for monitoring one or more parameters associated with the developer solution and the waves utilized for agitation. For example, a thermal sensor is used to monitor a temperature associated with the developer solution during agitation. The thermal sensor feeds back such thermal information to a control system which may use such feedback data to modify one or more control signals used to control various properties of the waves (e.g., magnitude, frequency, or direction). Alternatively, a wave sensor is used to monitor one or more properties associated with the waves being produced to agitate the developer solution. The wave sensor feeds back such wave data to a control system which may use such feedback data to modify one or more control signals used to control various properties of the waves. Consequently, the present invention contemplates a dynamic feedback feature which allows a modulated agitation of the developer solution to maximize the benefits associated therewith.
To the accomplishment of the foregoing and related ends, the invention 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: 5455894 (1995-10-01), Conboy et al.
patent: 5555234 (1996-09-01), Sugimoto
patent: 5625433 (1997-04-01), Inada et al.
patent: 5858475 (1999-01-01), Chiu
patent: 5876875 (1999-03-01), Chiu
patent: 5962070 (1999-10-01), Mitsuhashi et al.
patent: 5984540 (1999-11-01), Mimasaka et al.
patent: 6010255 (2000-01-01), Chiu
“Wafer Defect Reduction, Unpatterned Wafer Inspection, Surfscan®SP1”, Copyright © 2000 KLA-Tencor Corporation. Taken from web sitehttp://www.kla-tencor.com/p
Phan Khoi A.
Rangarajan Bharath
Chaudhuri Olik
Eschweiler & Associates LLC
Garcia Joannie Adelle
LandOfFree
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