In Focused Ion Beam (FIB) TEM sample preparation, polymer tends to bend, roll and melt under FIB induced thermal stress [1]. Actually, delamination of the stacked metal and polymer layers can be possible. 

Sample-mount method can result in different bending characteristics. For instance, as shown in Figure 1229, side-mount polymer lamella develops very strong bending, so that further thinning is not possible. However, bottom-mount develops less bending.

(a)	(b)	(c)

[1] S. Kim et al., Ultramicroscopy, 111:191 – 199 (2011).
[2] X² STEM Lamella Preparation from Multi-composite Organic Electronic Devices with ZEISS FIB-SEMs, ZEISS.