ISSN 10637397, Russian Microelectronics, 2015, Vol. 44, No. 4, pp. 236–240. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © I.A. Glinskii, N.V. Zenchenko, 2015, published in Mikroelektronika, 2015, Vol. 44, No. 4, pp. 269–274.
Solidstate power amplifiers based on highpower
microwave transistors (HPMWTs), which provide
power magnitude from units to several tens of watts in
the L, S, and X wavelength ranges, are now the basic
element for use in transmitting channels of radar sta
tions, active electronically scanned arrays, and com
munication systems .
The key requirement for the HPMWT is that it
must provide the maximum absolute and specific
power with a high coefficient of efficiency for
increased working temperatures and the given param
eters of reliability.
When increasing the specific power, the problem of
heat removal from the active area of the transistor (to
prevent overheat) inevitably arises.
High temperatures negatively affect the parameters
of a device: frequency characteristics, output power,
and reliability . Therefore, when designing the elec
tronic device, it is required to take measures for
increasing the effectiveness of heat removal from the
active part of the crystal. An important stage in solving
this problem is simulation of temperature distribution
in the device.
The purpose of this work is to develop a procedure
for calculating the temperature distribution in the
electronic device, to evaluate the effect of the heat dis
tribution element (HDE) made of polycrystalline
CVD diamond on the temperature characteristics of
the device, and to calculate the parameters of the heat
HEAT DISTRIBUTION ELEMENT MADE
OF CVD DIAMOND
A steady increase in the power capacity of elec
tronic devices is accompanied by the strengthening of
requirements for cooling active elements. Heat sinks
are used to remove heat from the crystal . The effec
tiveness of cooling, however, depends not only on the
effectiveness of the heat sink itself but also on the
effectiveness of the whole heat distribution structure
(base of the heat sink, solder, and material of the semi
conductor crystal); in particular, it depends on the
effectiveness of heat transfer from the crystal to the
heat sink. The problem of increasing the effectiveness
of heat transfer from the crystal to the heat sink can be
solved by using the distributor of the heat flow or the
heat distribution element.
The HDE is a bonding interlayer between the active
crystal and the heat sink. The area of the HDE exceeds
that of the crystal, which enables distribution of the
heat flow from the crystal surface to the surface of the
heat sink, thus reducing its density.
The HDE must be made of material possessing
high thermal conduction: aluminum nitride ceramics,
beryllium ceramics, cooper, etc. Such HDEs, how
ever, do not always meet the requirements for heat
removal from the active area of the transistor taking
into account the increase in the power capacity of
modern semiconductor devices . Moreover, in
ultrahigh frequency devices, the use of metal as a
HDE can result in an unwanted parasitic capacity
between the crystal and the heat sink; therefore, it is
important that the HDE is made of dielectric material.
Computer Simulation of the Heat Distribution Element
for HighPower Microwave Transistors
I. A. Glinskii and N. V. Zenchenko
Institute of Ultrahigh Frequency Semiconductor Electronics, Russian Academy of Sciences, Russia
Received December 4, 2014
—A simulation procedure is proposed that allows one to find temperature distributions in elec
tronic devices and to evaluate thermal resistances for the whole device and for its individual structural ele
ments. The results of calculating the temperature distribution in a multifinger highpower microwave tran
sistor (HPMWT) are presented. In the case of the model under study, it is found that placing a heat distri
bution element (HDE) made of polycrystalline CVD diamond between the crystal and the heat sink reduces
the total thermal resistance of the transistor structure and decreases the overheat of the structure by approxi
mately 2%. For the model of the multifinger HPMWT, the dependences of the thermal resistance on the
thickness and width of the HDE are obtained. The HDE size optimal in terms of the minimum thermal resis
tance of the structure is found to be 6000
m. For the model of the multifinger HPMWT with
the HDE, the maximum temperatures in the area of heat release are compared for various values of convec
tion. Natural air convection is found to be sufficient for heat remove.