Adhesion Characteristics of Magnetron-Sputter-Deposited ... · 15 Goto et al.: Adhesion...
Transcript of Adhesion Characteristics of Magnetron-Sputter-Deposited ... · 15 Goto et al.: Adhesion...
12
Transactions of The Japan Institute of Electronics Packaging Vol. 5, No. 1, 2012
1. IntroductionTo realize copper wiring on resin materials with high
frequency signal propagation, low electrical power con-
sumption and high-density packaging, flat copper wiring
on a smooth resin material with a low dielectric constant
and a low dielectric loss is essential. Cycloolefin polymer
(COP) resin is a promising material which satisfies these
requirements, where its relative dielectric constant and
dielectric loss tangent are around 2.35 and an order of 10–4
for a wide frequency region within 70 GHz, respectively.[1]
Furthermore, COP has excellent low moisture absorption
characteristics. Thus, process technologies for realizing
copper wiring on the smooth COP surface have been stud-
ied.[2–5] Our group proposed adhesive copper seed-layer
formation processes on the smooth-surface COP using
magnetron sputtering as an alternative to the electroless
deposition which usually requires an intentional rough-
ness-induced process to obtain practical adhesion between
the resin and the metal. Rough surfaces degrade the sig-
nal propagation characteristics of wiring, especially as sig-
nal frequency increases, because the traveling length of
the electrical current, and hence conductor loss, increases
due to the decrease of skin depth which defines the level
of current flow from the metal surface. At the same time,
electroless deposition involves a heavy environmental
load. The adhesive seed layer can be obtained by introduc-
ing consecutive processes of plasma nitridation of the COP
surface, thin copper nitride film deposition, and copper
deposition by magnetron sputtering before the electroplat-
ing.[3, 4] Notably, because we have developed the novel
magnetron sputtering equipment called rotation magnet
sputtering which can realize high target utilization,[6] pro-
duction costs can be reduced compared to the use of con-
ventional magnetron sputtering equipment by realizing
high productivity. In this paper, characteristics of the pro-
posed adhesive COP-metal stacked layer are investigated
[Technical Paper]
Adhesion Characteristics of Magnetron-Sputter-Deposited Copper
on Smooth Cycloolefin for Realizing Wiring with High-Frequency
Signal PropagationTetsuya Goto*, Takatoshi Matsuo**, Masamichi Iwaki*, Kazuki Soeda*, Ryosuke Hiratsuka*, Shigetoshi Sugawa*,
and Tadahiro Ohmi*
*New Industry Creation Hatchery Center, Tohoku University, Sendai 980-8579, Japan
**R&D Center, ZEON Corporation, Kawasaki 210-9507, Japan
(Received July 23, 2012; accepted September 25, 2012)
Abstract
Copper wiring formation on a resin material with a low dielectric constant, a low dielectric loss and a smooth surface is
indispensable to realize high-frequency signal propagation with fine wiring patterns. Cycloolefin polymer (COP) resin is
a promising material to meet these requirements. We propose adhesive copper seed layer formation on the COP by
magnetron sputtering as an alternative to the electroless deposition which usually requires an intentional roughness-
induced process to obtain practical adhesion between the resin and the metal. The proposed process steps include plasma
nitridation of the COP surface, thin CuN film deposition and Cu film deposition before the electroplating. Excellent adhe-
sion strength between the COP and the metal, greater than 1 kN/m, can be obtained while maintaining a smooth surface,
which is attributed to the strong chemical bond generated between the nitrided COP surface and the CuN film. The
coplanar transmission line was fabricated using the proposed process steps with semi-additive processes, and we found
that the introduction of relatively high-resistive CuN film does not cause degradation of the propagation characteristics.
Keywords: Cycloolefin Polymer, Magnetron Sputtering, Seed layer, Copper Wiring, Coplanar Line, Propagation
Loss
13
Goto et al.: Adhesion Characteristics of Magnetron-Sputter-Deposited Copper (2/8)
in detail to gain further understanding of the mechanism
of generating excellent adhesion. Also, the high frequency
propagation characteristics of the coplanar transmission
line fabricated using the proposed process steps are pre-
sented.
2. Experimental SetupFigures 1(a) and 1(b) show the cross-sectional structure
of the newly developed rotation magnet sputtering and the
bird’s eye view of its magnet system, respectively.[6] The
magnet system includes helical magnets with alternative
polarities, and multiple moving plasma loops are excited at
the target surface by rotating the helical magnets using a
motor. This results in full erosion of the target surface, and
easily realizes a high target utilization, larger than 60%,
much better than the 30% realized in typical conventional
fixed rectangular magnet systems. In the experiment, a
rectangular 6-mm-thick copper target (350 mm × 112 mm)
was used. The width of the deposition region, which is
defined by a slit formed by a electrically grounded plate as
shown in Fig. 1(a), was 60 mm. A 0.1-mm-thick COP sub-
strate with a typical size of 50 mm × 100 mm was set on a
movable grounded stage below the target, and the film
deposition as well as the plasma treatment, such as plasma
nitridation, were performed by scanning the movable
stage through this deposition region. The moving speed of
the stage was set at 8 mm/s. Figure 2 shows the proposed
seed layer formation steps before the Cu electroplating.
The plasma nitridation was carried out by Ar/N2 plasma
with various N2 additive ratios [ratios of N2 flow rate to the
total flow rate (400 sccm in the experiment)]. The movable
stage was scanned two times for the plasma nitridation,
which corresponds to a plasma irradiation time at an arbi-
trary position of the COP substrate of 15 seconds. Hereaf-
ter, process time will be described in this way. Working
pressure in the chamber was 52 Pa. A 13.56 MHz-rf power
was applied to the Cu target with a power density of 0.25
W/cm2. Since this power density was small and working
pressure was relatively high compared to the typical pres-
sure for film depositions, the target bias voltage generated
was small. Thus, the sputtering of the Cu target and result-
ing film deposition on the COP surface were negligibly
small, at least in the short plasma treatment time of 15 sec-
onds. After the plasma treatments, a CuN film with a thick-
ness of 35 nm was deposited on the COP surface by reac-
tive sputtering for the condition of Ar/N2 = 490/210 sccm
with a total pressure of 0.67 Pa. The deposition time was 15
seconds. Then, Cu with a thickness of 280 nm was depos-
ited for an Ar flow rate of 585 sccm with a working pres-
sure of 0.67 Pa. The deposition time was 90 seconds. In
these depositions of CuN and Cu, dc power was applied to
the target with a power density of 1.26 W/cm2. After the
seed layer deposition, the samples were unloaded from the
magnetron-sputtering chamber, and Cu with a thickness of
22 μm was deposited by electroplating.
Adhesion strength, the force required per width (5 mm)
to peel the Cu film at 30 mm/min, was measured using a
peel testing machine. Scanning electron microscopy
(SEM), energy dispersive X-ray spectroscopy (EDX), X-ray
photoelectron spectroscopy (XPS), atomic force micros-
copy (AFM), and a contact angle measurement machine
were used to characterize the samples.
The coplanar transmission line was fabricated on the
COP surface using the widely used semi-additive method.
The seed layer was formed using the proposed process
steps. Then, a dry-film resist was laminated on the seed
layer surface, and that was followed by photo-lithography Fig. 1 (a) A cross sectional structure of the newly developed rotation magnet sputtering and (b) its magnet system.
Fig. 2 The proposed seed layer formation steps before the Cu electroplating.
14
Transactions of The Japan Institute of Electronics Packaging Vol. 5, No. 1, 2012
patterning of the dry-film resist. Then, Cu electroplating
was carried out, and that was followed by wet etching of
the dry-film resist. Finally, the exposed seed layer was
eliminated by slight wet etching to isolate the wiring pat-
tern. The high-frequency propagation characteristics were
measured using the network analyzer (E8364B Agilent
Technologies) and the G-S-G probe (I50-A-GSG-150 Cas-
cade Microtech).
3. Results and Discussion3.1 Adhesion characteristics
Figure 3 shows the adhesion strength between the COP
resin and the metal as a function of the N2 additive ratio in
the plasma nitridation processes. The samples were fabri-
cated by the process steps shown in Fig. 2. The N2 additive
ratio was changed from 0% to 60%, while the total gas flow
rate was kept at 400 sccm. Note that the N2 additive ratio of
0% means that the COP surface was irradiated by pure Ar
plasma, so there is no nitridation of the COP surface. In
addition, a case without the introduction of CuN film depo-
sition was carried out in the pure Ar-plasma treated case
(i.e., the Cu seed layer was deposited after pure Ar plasma
treatment), and plotted in Fig. 3, showing very poor adhe-
sion strength around 0.1 kN/m. On the other hand, when
the CuN film is introduced, adhesion strength improves
drastically to about 0.8 kN/m even in the pure-Ar plasma
treated case. Furthermore, by introducing the Ar/N2
plasma treatment, a strong adhesion of 1 kN/m or more
can be obtained for the N2 additive ratio of at least 15% or
more, as shown in Fig. 3. The results show that the intro-
duction of both plasma nitridation and the CuN film is
indispensable to obtain excellent adhesion. Figures 4(a)–
4(e) show the surface morphology of the COP resin sur-
face for the 1 μm × 1 μm area evaluated by AFM. The
result of the initial COP surface is shown in Fig. 4(a), and
Figs. 4(b)–4(e) show the cases of plasma treatments with
the N2 additive ratios of (b) 0% (pure Ar plasma treatment),
(c) 15%, (d) 30% and (e) 60%, respectively. In the plasma
treated case, the AFM measurements were carried out
after the removal of the Cu film (and of the CuN film)
formed on the COP by wet etching using hydrated ferric
oxide. Surface roughness, Ra, and the peak-to-valley
length, P-V, obtained from the measured data are also indi-
cated in the figure. Surface roughness, Ra, is defined by
the following surface integral over the measurement field:
RS
z x y Z dxdya AVE= ( ) − ∫∫1, , (1)
Fig. 3 Adhesion strength between the COP resin and the metal as a function of N2 additive ratio in the plasma nitrida-tion processes.
Fig. 4 The surface morphology of the COP resin surface for the area of 1 μm × 1 μm evaluated by AFM. The result of the initial COP surface is shown in (a), and (b)–(e) show the cases of plasma treatments with the N2 additive ratios of (b) 0% (pure Ar plasma treatment), (c) 15%, (d) 30% and (e) 60%, respectively.
15
Goto et al.: Adhesion Characteristics of Magnetron-Sputter-Deposited Copper (4/8)
where S is the area of the measurement field, z(x, y) is the
height at position (x,y) and ZAVE is the averaged height in
the measurement field. It is found that both Ra and the P-V
can be maintained at very low levels, around 0.5 nm and
less than 10 nm, respectively, even after the plasma treat-
ments and film depositions, demonstrating that the plasma
treatment does not significantly roughen the COP surface.
Figures 5(a)–5(d) show SEM images and EDX mappings
of surfaces of the stripped metal (Cu or CuN/Cu) films.
Measurements were carried out for the metal-COP-inter-
face side of the metal films stripped from the COP resin, as
illustrated in the bottom of the figure. Figure 5(a) shows
the case of the N2 additive ratio of 0% (pure Ar plasma
treatment) without introducing CuN film, while Figs. 5(b)–
5(d) show the cases of the N2 additive ratios of (b) 0%, (c)
30%, (d) 60% with CuN film, respectively. The adhesion
strengths of these samples were measured at (a) 0.1
kN/m, (b) 0.8 kN/m, (c) 1.2 kN/m and (d) 1.3 kN/m, as
shown in Fig. 5. The atomic compositions at the surface of
the stripped metal films were investigated by EDX mea-
surements for the regions defined by dotted lines in each
of the SEM images. The resulting EDX mappings of C and
Cu are shown at the bottoms of the SEM images, where
the colors are brighter as the amounts of C and Cu are
higher. Note that even when the CuN film was present, the
N component was under the detection limit of EDX
because of the thinness of the CuN film. Clear differences
of the surface structures of the stripped metal films and
the relative amounts of C on them were observed for the
different cases as follows. In the poor adhesion case (0.1
kN/m), where only the Ar plasma treatment was carried
out and the CuN film was not introduced [Fig. 5(a)], the
surface of the stripped Cu film is very smooth. However,
when the CuN film is introduced, adhesion strength
improves drastically to 0.8 kN/m even with the Ar plasma
treatment [Fig. 5(b)], and it seems from Fig. 5(b) that the
surface roughness of the stripped metal and relative
amount of C increases slightly. When both the Ar/N2
plasma treatment with an N2 additive ratio of 30% and the
CuN film are introduced, the adhesion strength improves
to 1.2 kN/m [Fig. 5(c)]. In this case, island shaped clus-
ters are observed on the surface in the SEM image, and
the corresponding EDX mapping indicates that these clus-
ters consist of C. Thus, it is expected that the clusters con-
sist of COP resin. When the N2 additive ratio is further
increased to 60%, where the maximum adhesion strength
of 1.3 kN/m is obtained [Fig. 5(d)], the amount of C is the
maximum of all the cases, and a very rough surface with a
dimple-like structure is observed. It is expected from
these results that the entire surface is covered with the
COP resin in the case shown in Fig. 5(d). This also sug-
gests that the peeling takes place at the inside of the COP
resin for the entire region, because the adhesion strength
is better than the mechanical strength of the COP. On the
other hand, for the poor adhesion case shown in Fig. 5(a),
the amount of C on the film is relatively small and a very
smooth surface can be seen in the SEM image, indicating
that the peeling takes place between the COP resin and
the metal layer due to poor adhesion. It is noted that the
surface morphologies of the clusters seen in Fig. 5(c) and
the entire surface seen in Fig. 5(d) are clearly different,
where the surface in the latter case is very rough with the
dimple-like structure described above. Although the rea-
son is not clear at present, the dimple-like structure might
result from the generation of strong tension inside the
COP resin during the peel test due to the strong adhesion.
As for the Cu component in the EDX measurement, there
Fig. 5 SEM images and EDX mappings of surfaces of the stripped metal (Cu or CuN/Cu) films. Measurements were carried out for the metal-COP-interface-side of the metal films stripped from the COP resin, as illustrated in the bottom of the figure. (a) shows the case of the N2 additive ratio of 0% (pure Ar plasma treatment) without introducing CuN film, while (b)–(d) show the N2 additive ratios of (b) 0%, (c) 30%, (d) 60% with introducing CuN film, respectively.
16
Transactions of The Japan Institute of Electronics Packaging Vol. 5, No. 1, 2012
are no significant differences between the various cases,
indicating that the thickness of the attached C layer is suf-
ficiently thinner than the measurement depth of EDX,
which is a few μm.
3.2 Measurements of plasma-treated COP surfaceTo investigate chemical changes in the COP surface
induced by the plasma treatment, XPS was carried out for
the COP surface after the plasma treatment; i.e., the
plasma-treated COP films without Cu and CuN film deposi-
tions were applied to the XPS measurements. Figure 6(a)
shows the atomic composition ratios of the COP surface as
a function of the N2 additive ratio in the 15-second plasma
treatment, which is the same condition as that in the sam-
ple fabrication for the adhesion measurements. The initial
atomic composition ratios before the plasma treatment are
also shown. The take-off angle of the secondary electron
was set at 45° in the XPS measurement. Note that a small
amount of Cu with a composition ratio less than 1% (near
the detection limit) is observed in the plasma-treated case
(which is not indicated in the graph). N is observed in the
Ar/N2 plasma treatment case, suggesting the nitridation of
the COP surface. In the case of the pure Ar plasma treat-
ment, the O component increases to about 10% from the
initial state of about 5%. It is believed that such an increase
of the O component is mainly induced by oxidation of dan-
gling bonds at the COP surface generated by the plasma
irradiation, which occurs with air exposure after the sam-
ple is unloaded (thus, this phenomenon is not related to
the in-situ processes where the seed layer is deposited
after the plasma treatment without air exposure). When
the N2 additive ratio increases, however, the O component
decreases as shown in Fig. 6(a). The results suggest that
the nitridation of the COP surface can effectively prevent
the COP surface from being oxidized even in air after
unloading the sample. Figure 6(b) shows the C1s photo-
electron spectra from the XPS measurements for the initial
sample, the pure Ar-plasma treated sample, and the Ar/N2
(30%)-plasma treated sample. A hump on the high-energy
side (around 290 eV) of the tail of the main spectral peak
can be clearly seen only in the Ar/N2–plasma treated case.
It has been confirmed that similar tails were also found for
the other N2 additive ratios, 15% and 60%. The results sug-
gest that these tail components result from the nitridation
of the COP surface. These XPS data, shown in Fig. 6, were
obtained for the surface of the COP. We also measured
depth profiles of the XPS data with the widely used in-situ
Ar ion beam etching technique. Figure 7 shows the depth
profiles of the photoelectron spectra of C1s, N1s and O1s
for the Ar/N2 (30%)-plasma treated sample. The spectra for
each atomic orbital of the topmost layer of the resin are
shown at the top of the figure, and the spectra of the next
three layers inside from the topmost layer are shown in
order in Fig. 7. The spectra of the inside layers were
obtained by cyclic Ar ion beam etchings and the XPS mea-
surements. The Ar ion beam flux density was set to corre-
spond to an etching depth of 1 nm in the case of SiO2 for
one cycle, which is a rather small etching rate. It is found
from Fig. 7 that the hump structure at the C1s photoelec-
tron spectrum and the spectral peak of the N1s photoelec-
tron spectrum are only observed in the topmost layer, and
these features are not observed for the second or deeper
layers after the Ar ion beam etching. These results sug-
gest that the thickness of the nitrided layer of the COP is
very thin with an order of nm.
We also checked the wettability of the COP surface after
the plasma treatment. It is generally difficult to discuss a
relationship between wettability and adhesion, especially if
the adhesion layer is formed by dry processes such as
Fig. 6 (a) Atomic composition ratios of the COP surface as a function of the N2 additive ratio in the plasma treatment for 15 seconds. (b) C1s photoelectron spectra in the XPS measure-ments in the cases of the initial sample, pure Ar-plasma treated sample and the Ar/N2 (30%)-plasma treated sample.
Fig. 7 The depth profiles of photoelectron spectra of C1s, N1s and O1s for the Ar/N2 (30%)-plasma treated sample.
17
Goto et al.: Adhesion Characteristics of Magnetron-Sputter-Deposited Copper (6/8)
sputtering depositions. However, since surface chemical
changes can be quickly and easily checked, the wettability
measurements were carried out. Figures 8(a) and 8(b)
show the water contact angle of the COP surface as a func-
tion of (a) the N2 additive ratio in the 15-second plasma
treatment and (b) the nitridation time for the N2 additive
ratio of 30%, respectively. The contact angle of the COP
surface without plasma treatment was 99°, as denoted in
Fig. 8(a) and Fig. 8(b) (the value at 0 seconds). Since the
COP resin consists of nonpolar hydrocarbons, the wettabil-
ity of the COP resin is low, and thus, the contact angle of
the initial state is high (99°). It is found from Fig. 8(a) that
wettability increases and thus the contact angle decreases
with the plasma treatment. The contact angle in the pure
Ar-plasma treated case decreases to about 80° from the
initial angle of 99°, and further reduction to about 40° is
observed in the plasma-nitrided case. It is empirically
found that the inclination of the N2-additive-ratio depen-
dence of the reduction of the contact angle is qualitatively
similar to that of the increase of the adhesion strength in
the case of introducing the CuN film shown in Fig. 3. Since
the surface roughness can be kept low even after the
plasma treatment, as shown in Fig. 4, the change in the
contact angle is induced by a change in the chemical struc-
ture of the COP surface, not by an increase of surface
roughness. Because both nitridation and oxidation
increase polarity at the COP surface, the water contact
angle will decrease with such chemical structure changes.
Since the XPS results indicate the post oxidation of the
COP surface in the Ar-plasma treated case, it is considered
that the reduction of the contact angle observed in the
pure Ar-plasma case is induced by the post oxidation, and
that the further reduction of the contact angle obtained in
the Ar/N2-plasma treated case is induced by plasma nitrid-
ation at the COP surface. As for the nitridation time depen-
dence, Figure 8(b) shows that the contact angle decreases
steeply to 40° for the nitridation time of around 15 sec-
onds, and increases slightly and asymptotically approaches
about 55°. Although the reason of this asymptotic value is
not clear at present, the results suggest that the nitridation
time of 15 seconds is sufficient to obtain an effective
nitrided COP surface.
3.3 Coplanar transmission lineThe proposed metallization processes described above
were applied to the fabrication of a coplanar transmission
line in order to evaluate the electrical performance of wir-
ing. Figure 9 shows a SEM image of the pad region of the
fabricated coplanar transmission as well as its schematic
cross-sectional structure. The width of the signal line and
the spacing between the signal line and the ground were
200 μm and 20 μm, respectively, which corresponds
approximately to the characteristic impedance of 50 Ω.
The length of the coplanar line was 2 cm, and the Cu thick-
ness was 12 μm. Widely used semi-additive processes
were successfully applied to the fabrication of the coplanar
line with CuN and Cu film deposition by magnetron sput-
tering as the seed layer as shown in Fig. 9. The existence
of the CuN film increases the total resistivity of the wiring
and thus might degrade its electrical properties. There-
fore, it is important to evaluate the effect of the introduc-
tion of CuN. It has been already confirmed that CuN resis-
tivity increases with an increase of the N2 additive ratio in
the rf-dc coupled sputtering.[3] In this study, the CuN film
was deposited by dc sputtering to reduce the heat flux on
the COP substrate. We have also confirmed that the behav-
ior of the resistivity in the dc-sputtering case is similar to
Fig. 8 The water contact angle of the COP surface as a func-tion of (a) N2 additive ratio in the plasma treatment for 15 sec-onds and (b) nitridation time in the case of the N2 additive ratio of 30%, respectively.
Fig. 9 A SEM image of pad region of the fabricated coplanar transmission as well as its schematic cross-section structure.
18
Transactions of The Japan Institute of Electronics Packaging Vol. 5, No. 1, 2012
that in the rf-dc coupled sputtering case, and that the resis-
tivity is about 18 μΩcm in this study, which is about 10
times higher than the pure Cu resistivity of 1.8 μΩcm. To
overestimate the effect of introducing the high-resistive
CuN film, the thickness of the CuN film was set at 0.14 μm
which was 4 times thicker than that in the case of the
aforementioned adhesion measurements. Figure 10 shows
the frequency dependence of the propagation loss (S21
parameter) per wiring length of the fabricated coplanar
line in the cases with and without the introduction of CuN
film. Note that since the COP surface was nitrided before
seed layer formation in both cases, the metalizing adhe-
sion even in the case without the CuN film was adequate to
at least measure the electrical properties by making the
G-S-G probe contact the pad of the coplanar line. It is found
that a signal propagation of –0.3 dB/cm at around 10 GHz
can be achieved in both cases, and also, no significant dif-
ference between the two cases is observed for the wide
frequency region within 50 GHz. It is well known that
when the frequency increases, the electrical current flows
mainly at the surface of the conductor, between the outer
surface and a level called the skin depth defined by δ ωµσ= 2 / , where ω is the angular frequency of the cur-
rent, μ is the absolute magnetic permeability of the con-
ductor, and σ is the conductivity of the conductor.[7] The
skin depth decreases as the frequency increases, and is
about 0.3 μm at 40 GHz (if a Cu conductivity value of 58 × 106
S/m is used), which is comparable to the thickness of the
CuN film. In the case of the coplanar line, however, the
electrical current mainly flows at the sidewall of the wiring
including the 12 μm-thick electroplated Cu layer. This
might be a main reason for no degradation of the propaga-
tion properties even when introducing the relatively-high
resistive CuN film.
4. ConclusionTo realize Cu wiring with high-speed signal propagation,
low electrical power consumption, and high density pack-
aging, adhesive copper seed layer formation processes
using magnetron sputtering technology was developed for
metallization on a smooth COP resin with good high-fre-
quency electrical properties such as low dielectric loss and
a low dielectric constant. By introducing the proposed in-
situ processes including plasma nitridation, thin CuN film
deposition, and Cu film deposition before the electroplat-
ing, excellent adhesion capability can be obtained. It is
found that the smooth surface of the COP can be main-
tained even when introducing the proposed plasma pro-
cesses, and thus, the excellent adhesion is attributed to the
strong chemical bond between the nitrided COP surface
and the CuN film. The XPS results and the water contact
angle measurements suggest the nitridation of the COP
surface. The proposed seed layer formation processes do
not use electroless plating, which requires an intentional
roughness-inducing process to obtain practical adhesion
between the resin and the metal, and entails a heavy envi-
ronmental load as well. A coplanar transmission line was
fabricated using the proposed seed layer formation pro-
cesses with the semi-additive processes, and we found that
the introduction of relatively-high resistive CuN film does
not cause degradation of the signal propagation character-
istics for the wide frequency region within 50 GHz. The
proposed technology will greatly contribute to next-gener-
ation fine wiring on resin materials with high-frequency
signal propagation.
References[1] S. Kaneko, Y. Kobayashi, and Z. Ma, “Heikougataen-
bankyousinki no sokuteigenkai ni kansuru kentou,”
IEICE Technical Report MW2010-79(2010-09), 2010
(in Japanese).
[2] H. Imai, M. Sugimura, M. Kawasaki, A. Teramoto, S.
Sugawa, and T. Ohmi, “High-Frequency Propagation
on Printed Circuit Board Using a Material With a Low
Dielectric Constant, a Low Dielectric Loss, and a Flat
Surface,” IEEE Trans. Components and Packaging
Technol., Vol. 32, pp. 415–423, 2009.
[3] T. Ohmi, T. Goto, H. Imai, M. Sugimura, and O.
Kawashima, “Proposal of Very High Performance and
High Density Printed Wiring Board and Its Very High
Productivity Manufacturing Processes,” IEEE Trans.
Components Packaging and Manufacturing Technol,
Vol. 1, Issue 4, pp. 486–494, 2011.
Fig. 10 A frequency dependence of propagation loss (S21 parameter) per wiring length of the fabricated coplanar line in the cases with and without the introduction of CuN film.
19
Goto et al.: Adhesion Characteristics of Magnetron-Sputter-Deposited Copper (8/8)
[4] T. Goto, O. Kawashima, and T. Ohmi, “Adhesive Cop-
per Seed Layer Formation as an Alternative to Elec-
troless Deposition for Printed Wiring Board Fabrica-
tions by Rotation Magnet Sputtering,” International
Conference on Electronics Packaging 2010, TC3-1,
Sapporo, May 2010.
[5] K. Baba, Y. Nishimura, M. Watanabe, and H. Honma,
“Formation of Fine Circuit Patterns on Cyclo Olefin
Polymer Film,” Transaction of The Japan Institute of
Electronics Packaging, Vol. 3, No. 1, pp. 73–77, 2010.
[6] T. Goto, T. Matsuoka, and T. Ohmi, “Rotation magnet
sputtering: Damage-free novel magnetron sputtering
using rotating helical magnet with very high target
utilization,” J. Vac. Sci. Technol. A, Vol. 27, No. 4, pp.
653–659, 2009.
[7] R.E. Collin, Foundations for Microwave Engineering,
2nd Edition, McGraw-Hill, New York, 1992.
Tetsuya Goto was born in Chiba, Japan, in 1972. He received the B. S., M. S., and Ph.D. degrees in physics from Tsukuba University, Ibaraki, Japan in 1995, 1997, and 2000, respectively. He researched physics of high-temperature plasmas in Tsukuba University. In 2000, he moved to Tohoku University
where he is currently an Associate Professor in the New Industry Creation Hatchery Center, Tohoku University. He is currently engaged in advanced semiconductor process technologies includ-ing sputtering film depositions, plasma-enhanced chemical vapor depositions, and plasma etchings for semiconductor devices and packages, and flat panel displays.
Takatoshi Matsuo was born in Osaka, Japan, on December 4, 1981. He received the B. S. and M. S. degrees in material engi-neering from Tokyo Institute of Technology, Tokyo, Japan in 2004 and 2006.He joined Zeon Corporation, Tokyo, Japan, in 2006. In 2006–2012, he has been engaged in the research and development of new materials used in semiconductors.
Masamichi Iwaki was born in Hokkaido, Japan, in 1982. He received the B. S. and M. S., degrees in engineering from Hiroshima University, Higashihiroshima, Japan in 2006, and 2008, respectively. He joined NIPPON VALQUA INDUSTRIES, LTD., Tokyo, Japan, in 2008. In 2010-2012, he has been seconded to the New Industry Creation Hatchery Center, Tohoku University as a researcher. He was engaged in surface modification by plasma treatment. He is currently engaged in the development of sealing materials for semiconductor manufacturing equipment.He is a member of the Japan Society for Analytical Chemistry.
Kazuki Soeda was born in Hyogo, Japan, on June 9, 1980. He received the B. S. and M. S. degrees in engineering from Univer-sity of Shiga prefecture, Shiga, Japan, in 2003 and 2005, respec-tively. He joined Nichias Corporation, Shizuoka, Japan, in 2005. He is currently engaged in the development of inorganic fiber insulation technology.
Ryosuke Hiratsuka was born in Saga, Japan, on August 10, 1984. He received the B. S. and M. S. degrees in engineering from Kyushu Institute of Technology, Fukuoka, Japan, in 2008 and 2010, respectively. He joined Nichias Corporation, Shizuoka, Japan, in 2010. He is currently engaged in the study of surface modification of fluorine resin.
Shigetoshi Sugawa received his M. S. degree in 1982 in Physics from the Tokyo Institute of Technology and his Ph.D. degree in 1996 in Electrical Engineering from Tohoku University. During 1982–1999, he worked in Canon Inc., where he researched high S/N ratio solid-state imaging devices
and other electronic devices. In 1999, he moved to Tohoku Uni-versity and he is currently a professor at the Graduate School of Engineering, Tohoku University. He is currently engaged in researches on CMOS image sensors, high-performance ULSIs and advanced displays.
Tadahiro Ohmi was born in Tokyo, Japan, in 1939. He received the B. S., the M. S., and Ph.D. degrees in electrical engineering from Tokyo Institute of Technology, in 1961, 1963, and 1966, respectively. In 1972, he moved to Tohoku University. He was a Full Professor with Department of Electronics, Faculty of
Engineering in 1985, with Department of Electronic Engineering, Graduate School of Engineering in 1997, and with New Industry Creation Hatchery Center, Tohoku University in 1998. Dr. Ohmi has been a Senior Research Fellow with the New Industry Cre-ation Hatchery Center, Tohoku University since 2011. From 1972, He is engaged in researches on high-performance ULSI, high-speed flat-panel display, and advanced semiconductor process technologies based on ultraclean technology concept. His research activities are summarized as 1,400 original papers and 1,700 patent applications.