Direct e-beam lithography of PDMS

19 In this paper, the viability of directly exposing thin films of liquid poly(dimethylsiloxane) (PDMS) to elec20 tron beam (e-beam) irradiation using e-beam lithographic methods for the purpose of creating perma21 nent micro-scale components has been investigated. By exposing 1.1 lm thickness PDMS films to 22 doses in the range 10–50,000 lC/cm, it was discovered that the structure of the resultant film exhibits 23 four distinct phases, depending upon the exposure dose. These phases were manifested in both the resul24 tant Young’s modulus and thickness of the developed film. It was found that there is a critical dose 25 whereupon the resultant film undergoes solidification and adheres to the counter surface sufficiently 26 to survive the development process. It has been shown that the Young’s modulus of the solid film can 27 be varied over seven orders of magnitude, from that of a viscoelastic material through a rubbery regime 28 to that of a glassy one, by increasing the e-beam dose. At higher doses, excessive backscattering was 29 observed, as well as film swelling, resulting in poor spatial resolution. 3