1063-7397/00/2906- $25.00 © 2000 MAIK “Nauka /Interperiodica”
Russian Microelectronics, Vol. 29, No. 6, 2000, pp. 368–375. Translated from Mikroelektronika, Vol. 29, No. 6, 2000, pp. 417–425.
Original Russian Text Copyright © 2000 by Vorob’eva, Moskvichev.
More and more stringent demands for interconnect
density and system complexity, as well as the need to
cut product prices, make designers use passive compo-
nents (load resistors and decoupling capacitors) as a
part of a multilayer interconnection (MLI) system.
Recent reviews and original works show that the
technology of multichip modules (MCMs) [1–3],
which is being extensively developed, is a very promis-
ing approach. These modules (which are of three types:
MCM-D, MCM-C, and MCM-L) satisfy miniaturiza-
tion and speed requirements and can well replace con-
ventional switching boards.
MCM-D devices employ thin ﬁlms deposited on a
ceramic, silicon, or metal substrate.
These modules are fabricated using two similar
design concepts. They are based on custom-made
boards either with a preset line impedance or with inte-
grated passive components.
If a switching board is impedance-matched with the
basic IC, reﬂections and distortions in the signal path
are absent at high frequencies. However, such matching
is hard to realize, since tolerances on the impedance of
traditional printed-circuit boards (PCBs) may be as
loose as 25%. This is explained by a number of process-
related factors: a spread in the thickness of an insulator,
undesired etching of interconnection tracks, etc. In
new-generation high-speed devices, impedance toler-
ances will likely to be decreased to 5% or less. This
necessitates a more stringent control of PSB fabrica-
The impedance value, in its turn, speciﬁes the inter-
connect density, which is limited by technology capa-
bilities (rated insulator thickness) and the type of signal
paths (strip or microstrip lines).
The use of appropriate materials (providing a
desired impedance) and processes has made it possible
to fabricate MCMs with passive components integrated
immediately into the board. Today, pilot structures with
integrated resistors are available. The incorporation of
low-value capacitors is basically also possible but has
not yet been demonstrated.
The IBM Corp. was the ﬁrst to apply the MCM tech-
nology . Since the mid-1970s, IBM has developed
advanced thin-ﬁlm processes and employed them in the
production of medium-powered and general-purpose
computers that operate at clock frequencies from 50 to
125 MHz. These technologies allow designers to
implement conform (nonplanar) high-density thin-ﬁlm
MLI systems with the industry’s least cost per unit con-
ductor length. IBM researchers believe that the technol-
ogy of choice in MCM production depends on a via for-
mation technique: reactive ion etching, polyimide pho-
tolithography, laser drilling, anodic oxidation,
Electrodeposition is today favored by many ﬁrms
engaged in MCM production [4, 5]. In this case, struc-
tures with vertical (stacked) vias can be made. Stacked
vias and staggered vias are shown in Fig. 1. Stacked
vias are of smaller size, and the distance between them
is also smaller. Therefore, they are preferable. Greater
technological costs amply repair themselves in
improved electrical performance. First, precision con-
trol of the impedance is provided, and second, the
power consumption decreases because of shorter signal
paths. For example, in a staggered via conﬁguration
with a dielectric thickness
m and metal thick-
m (Fig. 1b), the voltage drop increases
by 37.5% because of the longer interconnection track.
Additionally, nonvertical vias affect other electrical
parameters, such as impedance, signal travel time,
noise, etc. Therefore, processes that provide vertical
structures are of most interest. These are, in particular,
electrochemical processes, including electrochemical
deposition and anodizing. The former case, however,
implies the use of a seed electrode sublayer and add-on
(chip) passive components.
The AT&T Corp. is among the leaders in MCM-D
production. The company’s MCM-D process has been
Resistors Integrated into MCM-D Modules: Fabrication
A. I. Vorob’eva and K. V. Moskvichev
Belarussian State University of Information Science and Radio Engineering, ul. Brovki 17, Minsk, 220072 Belarus;
Received March 7, 2000
—A review of works where passive components are integrated into MCM-D modules is presented.
The process of incorporating thin-ﬁlm resistors into MCM-D structures and the performance of the resulting
systems are discussed.