The substrate bow in a large area processing (LAP) was simulated using a finite element analysis (FEA). The structures considered were aluminum (Al) and glass substrates of various thicknesses, and a coating from photosensitive film thickness. It was found that the deflection of a large area substrate, e.g. 400 mm square, could not always be obtained from the linear, small deflection theory even if the curvature might be small and the stress-strain behavior in the linear elastic regime. In this case, the nonlinear, large deflection theory had to be adopted. Also, the gravity effect on the weight of substrate turned out to be very significant and had to be incorporated as well. The simulation incorporating these two factors agreed well with the experimental data, which was generated by spin coating and curing the BCB formulation on Al substrates, 400/spl times/400/spl times/1.27 mm. As a means of flattening out the curvature, subjecting a vacuum underneath the substrate was simulated. Significant reduction of the substrate deflection was observed by applying only a very small vacuum. This result suggested that the use of double-stick tape on the bottom of the substrate, for example, might also be feasible to completely eliminate the bow.
[1]
T. Tessier,et al.
Approaches to cost reducing MCM-D substrate fabrication
,
1993,
Proceedings of IEEE 43rd Electronic Components and Technology Conference (ECTC '93).
[2]
T. G. Tessier,et al.
Cost Implications of Large Area MCM Processing
,
1994,
Proceedings of the International Conference on Multichip Modules.
[3]
F. J. V. Preissig.
Applicability of the classical curvature-stress relation for thin films on plate substrates
,
1989
.
[4]
Jang-Hi Im,et al.
Physical and Mechanical Properties Determination of Photo-BCB-Based Thin Films
,
1996
.
[5]
G. Stoney.
The Tension of Metallic Films Deposited by Electrolysis
,
1909
.
[6]
N. J. Salamon,et al.
Thin film stress from nonspherical substrate bending measurements
,
1991
.