535.8
POVOLOTSKIY A.V, MANSHINA A.A.,

IVANOVA T. YU., TVER'YANOVICH YU.S.,

*KIM D., *KIM M., *KWON S.C.
OPTIMIZATION OF METAL PRECIPITATION WITH LCLD
METHOD FOR MICROELECTRONICS DEVICES
Laser Research Institute, St. Petersburg State University
Ulianovskaya 5, Petrodvorets, 198504 St. Petersburg
e-mail: malina@home.rclph.spbu.ru
*Korea Institute of Machinery and Materials
Sangham-Dong 66, Changwon, Kyungham, Republic of Korea
Laser methods are of widely use in modern technology and industry
as they allow to provide high quality and efficiency of manufacturing proc-
esses. A sort of laser methods was developed for surface processing and
localized metallization of different materials. Such techniques are used in
microelectronics industry for creation of sensors, multifunctional micro
systems, hybrid electronics and optics, interconnections between integrated
circuit structures and so on.
Our investigation is focused on localized metallization of the insula-
tor surfaces with Laser-induced Chemical Liquid phase Deposition (LCLD)
method. LCLD method can be considered among others laser-assisted
methods as the most efficient and promising; moreover it does not require
sophisticated equipment or dangerous chemical elements.
LCVD method consists in localized influence of focused laser beam
on surface of the material covered by a thin layer of electrolyte solution.
Laser radiation initiates a chemical reaction resulted in reduction of metal
complexes to metals in the liquid electrolyte, followed by metal deposition
on a substrate with a high degree of adhesion. Laser focal volume deter-
mines a volume of chemical reaction and provides for high spatial resolu-
tion of the resulted metal structures (micrometer or sometimes sub-
micrometer range). Conductive surface metal structures (wires) can be cre-
ated in a process of laser direct writing when focused laser beam is scanned
on the surface of the material. Laser and scan parameters, type of substrate
and composition of the electrolyte solution determine the characteristics of
the resulted structures (morphology, size, conductivity), that is why inten-
sive study should forego the wide practical application of the LCVD
method.
In our experiments on metal deposition with LCVD method CW Ar+
laser ( = 488 nm) was used for precipitation of Cu from the electrolyte
solution on SiO2 substrate. The deposition of copper was a result of stan-
dard laser-assisted chemical reaction [1]:
[Cu(L4)]2+ + 2HCOH + 4OH- Cu0 + 4L + H2 + 2H2O + 2HCOO-

(where L is the complexing or chelating agent)
The temperature of the solution was thermostated to 293 K. It was
found no chemical reaction and as a result, no metal deposition with LCVD
method can be initiated under the temperature below 290 K. First experi-
ments were carried out in stationary mode when the sample was not moved
relatively the laser beam. The microscope objective X8 was used to focus
laser beam; the focus spot size was estimated to have a diameter about 20
m at 1/e2 intensity. The laser power was fixed at 200 mW and 250 mW.
Fig. shows the micro-photo of metal spots deposited from the elec-
trolyte solution by Ar+ laser. The metal spots in the fig. (a) are deposited at
laser power 250 mW for 30 s, 50 s and 70s (top-down correspondingly).
The metal spots depicted in fig. (b) were precipitated with laser beam of
lower power 200 mW during 5 min. In this case good repeatability of size
of metal spots is observed, the diameter of the spots was found to be about
100 m.
The effect of laser parameters and precipitation conditions on char-
acteristics of the deposited structures was studied in detail.



) )
Fig. Micro-photograph of metal spots.
The work is supported by the Korea Research Foundation Grant #
2005 - D00017.

1. K. Kordas, K. Bali, S. Leppavuori, A. Uusimaki, L. Nanai. "Laser direct
writing of copper on polyimide surfaces from solution". Applied Surface
Science. 154-155, 2000, 399-404


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