Indirect-Bonded Metallization of Aluminum Nitride
- PDF / 1,397,937 Bytes
- 12 Pages / 415.8 x 637.2 pts Page_size
- 90 Downloads / 361 Views
INDIRECT-BONDED METALLIZATION OF ALUMINUM NITRIDE M. GRANT NORTON Washington State University, Department of Mechanical and Materials Engineering, Pullman, WA 99164 ABSTRACT The use of aluminum nitride (AIN) as a substrate and packaging material for microcircuit applications is of present interest due to its many advantageous physical properties. A limitation to the widespread use of AIN is the lack of an adequate metallization system. The most common method of achieving high-integrity metallized ceramics is through the use of indirect-bonded metallizations. A wide range of intermediate bonding materials are used, for example glasses, oxide mixtures, and active metals. In this paper, the indirect-bonded metallization of AIN will be reviewed and discussed. Requirements which must be considered in producing successful metallizations include; wetting of the substrate and the metal by the intermediate phase and the reactivity between the intermediate phase and the substrate. The reactions which occur in many of the systems considered can be predicted by examination of thermodynamic data. INTRODUCTION Aluminum nitride (AIN) has produced a great deal of interest as a substrate material for microcircuit packaging applications due to its high thermal conductivity [1-61. The thermal conductivity of presently available AIN substrates is as high as 260 Wm-IK-1. The thermal conductivity of 96% A1 2 03, the most widely used substrate material, is in the range 10-30 Wm-IK-1. In the most simple approach to application AIN will replace surface-mount and pin-grid-array modules where substantial benefit may accrue from its order of magnitude better thermal conductivity. Structures with large heat sinks are already required to meet the present thermal specifications of some optical components. Since these thermal specifications determine the reliability of the components, significant improvements may be achieved by being able to specify a lower device temperature through the use of AIN. AIN also has a number of other physical properties that render it interesting for packaging applications: close coefficient of thermal expansion (CTE) match to silicon, high electrical resistivity, and moderately low dielectric constant [7,8]. A limitation in the more widespread use of AIN has been the lack of an adequate metallization system. For example, the limited availability of compatible thick film material systems has restricted the production of hybrid circuits based on AIN to low volume applications. The metallization system is required for mounting of the integrated circuit, for interconnection to other circuit components and in the case of ceramic packages for joining the package base and lid. Metallization can be classified into two major types-direct bonded and indirect bonded. Direct-bonded metallization is achieved without the use of a second or intermediate phase, for example, by pressing together very flat mating surfaces to achieve diffusion bonding [9-11]. The most common method of achieving high-integrity metallized ceramics is th
Data Loading...
