High Tg, Low Dielectric Constant Aromatic Benzoxazoles Containing Allylether Pendent Groups for Use in Microelectronic P
- PDF / 54,897 Bytes
- 4 Pages / 612 x 792 pts (letter) Page_size
- 114 Downloads / 193 Views
High Tg, Low Dielectric Constant Aromatic Benzoxazoles Containing Allylether Pendent Groups for Use in Microelectronic Packaging Max D. Alexander Jr., Thuy D. Dang, Christina E. Specker, Marlene Houtz, R.J. Spry, and Fred E. Arnold Polymer Branch, Materials and Manufacturing Directorate, Air Force Research Laboratory Wright-Patterson Air Force Base, Ohio 45433-7750, U.S.A ABSTRACT Next generation microelectronic packaging requirements are driving the need to produce increasingly lower dielectric constant materials while maintaining high thermal stability and ease of processing. Polymer candidates with exceptionally low dielectric constant (2.0-2.4), high thermal stability (degradation temperature higher than 400°C), high glass transition temperature (greater than 350°C), low water uptake (less than one percent), solubility in selected organic solvents, and low thermal expansion are all required. We have successfully synthesized and characterized several candidate polymers in an effort to address these needs. INTRODUCTION To meet these goals, we have focused on the production of low dielectric constant polymers based on a family of exceptionally thermally-stable benzoxazoles. In previous work we demonstrated the use of polymers based on the structure shown in Figure 1, for microelectronic packaging applications. (1) CF3
CF3
OH N
C
CF3
N
CF3 O
N
x
CF3
N
CF3
C O
C
O
O
y
Figure 1. Monohydroxy-6F-PBO-co-12F-PBO polymer. In this work we extend the concept toward designing chemical routes to impart insolubility to the system Monohydroxy-6F-PBO-co-12F-PBO polymer via post-processing. Highly fused ring structures, formed via intramolecular hydrogen bonding, were utilized for the enhancement of the glass transition temperature, while lowering of the dielectric constants of these polymeric structures was accomplished by the incorporation of perfluoroisopropyl groups along the polymer backbone. The design of post-polymer reactions to impart insolubility to select polymer candidates was based on the methodology of attachment of crosslinking sites to the polymer backbone. Aromatic benzoxazoles containing pendant allylether groups were synthesized from the parent structures. Upon heating, the polymer would undergo an intramolecular rearrangement reaction (Claisen rearrangement) at 260°C, resulting in a Tg enhancement by increasing the number of fused rings via intramolecular hydrogen bonding between the in situ-formed hydroxyl groups and the nitrogen atom of the adjacent benzoxazole group. At elevated temperature (~350°C), crosslinking of the allyl groups would occur, thus providing a mechanism for insolubility and dimensional stability of the polymer system. The N6.6.1
crosslinking density of the polymer system was controlled by partial allylation of the hydroxyl groups attached to the aromatic benzoxazoles with a view toward maintaining the low dielectric constant value, high glass transition temperature and the insolubility as well as the mechanical toughness of the polymer system after processing. A typical
Data Loading...
