Stabilized polymer film and its manufacture

Details Stabilized polymer film and its manufacture Stabilized polymer film and its manufacture

2001-08-09

2004-03-09

Choi, Ling-Siu (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S348000, C526S348100, C526S346000

Reexamination Certificate

active

06703462

ABSTRACT:

The present invention relates to a polymer film that is used in the manufacturing of future integrated circuits (“IC's”) and, in particular, to methods of making a polymer film that will retain their structural integrity during and after exposure to processes involved in the fabrication of IC's.
BACKGROUND
During the manufacturing of IC's, multiple layers of films are deposited. Maintaining the compatibility and structural integrity of the different layers throughout the processes involved in finishing the IC is of vital importance. In addition to dielectric and conducting layers, its “barrier layer” may include metals such as Ti, Ta, W, and Co and their nitrides and silicides, such as TiN, TaN, TaSixNy, TiSixNy, WNx, CoNx and CoSi Nx. Ta is currently the most useful barrier layer material for the fabrication of future IC's that use copper as conductor. The “cap layer” normally consists of dielectric materials such as SiN, SiON, TEOS, SiyOx, FTEOS, SiCOH, and SiCH.
Poly (para-xylylene) (“PPX”) thin films, which have low dielectric constants (“∈”), are found in various forms. PPX thin film has the repeating unit of (—CX
2
—C
6
H
4−n
Z
n
—X
2
C—)
N
, where X and Z are the same or different and each is H or a halide; n=0 to 4, and N is an integer denoting the number of repeating units, ranging from at least 10 to preferably at least 20, and more preferably at least 50. These films are useful in the manufacturing of future IC's for several reasons. PPX-F i.e. [(—CX
2
—C
6
H
4−n
Z
n
—X
2
C—)
N
, where X=F, Z=H, n=0, and N as defined above] films prepared from dimers have shown, through X-Ray Photo Spectroscopy (“XPS”), undetectable changes in chemical composition after annealing at 425° to 450° C. for two hours in a vacuum (Plano et al., MRS Symp. Proc., Vol 476, (1998)). In addition, using the bending beam technique, it has been shown that PPX-F films are dimensionally stable up to the same temperature range after the first thermal cycle (Ho et al., MRS Spring Meeting Proceeding, Section 06.9 (1999)). It is also known that PPX-F films adsorb less than 0.02-0.04% moisture at ambient temperatures.
Various attempts to integrate PPX-F thin films into IC's using Cu Dual Damascene processes have failed (Wary et al., Proc. 2
nd
Intl. DUMIC (1996); Wary et al., Semiconductor Int'l, 19(6) (1996); Lu et al., J. Mater. Res., Vol. 14(1) (1999); Plano et al., MRS Symp. Proc., Vol 476, (1998)). None of the previous studies teaches processes or methods to make PPX-F films that pass the Ta compatibility test. A compatibility test uses a sample consisting of a thin (50 to 200 Angstrom) barrier or cap layer, such as Ta or SiC over a dielectric layer, such as PPX-F, on a silicon wafer. The sample is then subjected to increasing temperatures at different lengths of time and the structural integrity of the film layers is recorded. In the previous tests, the Ta barrier layer failed after the sample was annealed at 350° C. for 30 minutes under inert conditions.
What is needed, therefore, is a method for integrating a PPX film into future IC's that maintains the film's stability and compatibility with other layers.
SUMMARY AND DETAILED DESCRIPTION
An object of the present invention is to provide a PPX film that is suitable for fabrication of IC's using the Cu Dual Damascene process.
Another object is to provide processing methods that will make a PPX film that is compatible with barrier layer materials used in the manufacturing of future IC's.
A further object is to provide processing methods that will make a PPX film that is compatible with cap layer materials used in the manufacturing of future IC's.
Another object is to provide processing methods that will make a PPX film that remains stable at the high temperatures encountered in the manufacturing of future IC's.
In one embodiment of the present invention, there is a polymer film suitable for the fabrication of future IC's. It is preferably prepared by the process of polymerization of diradical intermediates under a vacuum with a low system-leakage-rate, or an inert atmosphere or both. The inert atmosphere is preferably devoid of free radical scavengers or compounds containing active hydrogen. In a specific embodiment, the diradical intermediate has the general structure e-CX
2
—Ar—X
2
C—e, where X=H or F, Ar is an aromatic diradical containing 6 to 30 carbons, and e is a free radical having an unpaired electron. In additional specific embodiments, the aromatic diradical is C
6
H
4−n
—F
n
(where n=0 to 4), C
10
H
6−n
—F
n
(where n=0 to 6), C
12
H
8−n
—F
n
(where n=0 to 8), C
14
H
8−n
—F
n
(where n=0 to 8), or C
16
H
8−n
—F
n
(where n=0 to 8). In further specific embodiments, the repeat unit of the polymer is CH
2
—C
6
H
4
—H
2
C, CF
2
—C
6
H
4
—F
2
C, CF
2
—C
6
F
4
—F
2
C, CH
2
—C
6
F
4
—H
2
C, CF
2
—C
6
H
2
F
2
—CF
2
, or CF
2
—C
6
F
4
—H
2
C. In other preferred embodiments, the vacuum is lower than 100 mTorrs, and preferably below 30 mTorrs. In further specific embodiments, the system leakage rate is less than about 2 mTorrs per minute, preferably less than 0.4 mTorrs/minute. In another preferred embodiment, the polymer film has a melting temperature (“T
m
”) greater than its reversible crystal transformation temperature (“T
2
”), which is greater than its irreversible crystal transformation temperature (“T
1
”), which is greater than its glass transition temperature (“T
g
”). In an additional specific embodiment, the polymer film is a fluorinated or unfluorinated PPX film having a general structure of (—CX
2
—C
6
H
4−n
Z
n
—X
2
C—)
N
, where X=H or F, Z=H or F, n is an integer between 0 and 4, and N is the number of repeat units, greater than 10. Preferably, N is greater than 20 or 50 repeat units. In another embodiment, the PPX film is transparent and semicrystalline. In further specific embodiment, the PPX film is PPX-F, which has a repeating unit with the structure of CF
2
—C
6
H
4
—F
2
C.
Another preferred embodiment is a method for preparing the polymer films by polymerizing the diradical intermediates at temperatures at or below their melting temperatures and with a low feed rate. In specific embodiments for the preparation of PPX-F films, the temperature of the substrate is lower than −30° C. and preferably below −35° C. The feed rate may be lower than 1.0 mMol/minute and preferably below 0.05 mMol/minute. In a specific embodiment, the method uses diradical intermediates with the general structure e—CX
2
—Ar—X
2
C—e, where X=H or F, Ar is an aromatic diradical containing 6 to 30 carbons, and e is a free radical having an unpaired electron. In additional specific embodiments, the aromatic diradical used is C
6
H
4−n
—F
n
(where n=0 to 4), C
10
H
6−n
—F
n
(where n=0 to 6), C
12
H
8−n
—F
n
(where n=0 to 8), C
14
H
8−n
—F
n
(where n=0 to 8), or C
16
H
8−n
—F
n
(where n=0 to 8). In further specific embodiments, the repeat unit of the polymer created by the method is —CH
2
—C
6
H
4
—H
2
C—, —CF
2
—C
6
H
4
—F
2
C—, —CF
2
—C
6
F
4
—F
2
C—, —CH
2
—C
6
F
4
—H
2
C—, —CF
2
—C
6
H
2
F
2
—CF
2
—, or —CF
2
—C
6
F
4
—H
2
C—. In other preferred embodiments, the vacuum utilized is lower than 100 mTorrs, and preferably below 30 mTorrs. In further specific embodiments, the system leakage rate is less than about 2 mTorrs per minute, preferably less than 0.4 mTorrs/minute. In another preferred embodiment, the polymer film produced by the method has a melting temperature (“T
m
”) greater than its reversible crystal transformation temperature (“T
2
”), which is greater than its irreversible crystal transformation temperature (“T
1
”), which is greater than its glass transition temperature (“T
g
”).
In an additional specific embodiment, the method generates a fluorinated or non-fluorinated PPX film having a general structure of (—CX
2
—C
6
H
4−n
Z
n
—X

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