LAYER-BY-LAYER IMAGING OF DIBLOCK COPOLYMER FILMS WITH A SCANNING ELECTRON-MICROSCOPE

We present a novel technique which allows for the investigation of blo ck copolymer microstructures on various substrates and at different de pths. Using a low voltage, high resolution scanning electron microscop e (SEM), we examined the topography and underlying morphology of poly( styrene)-poly(butadiene) diblock copolymer films. The internal morphol ogy of the film was exposed for SEM imaging by using a non-selective f luorine-based reactive ion etching (RIE) technique. By controlling the depth of the RIE etch we removed the surface layer of poly(butadiene) and exposed the microphase separated structure underneath for SEM ima ging. After obtaining SEM images of this exposed layer, we subsequentl y removed this layer with further RIE to obtain SEM images of the laye r underneath. By continuing this procedure, we can obtain images of th e microstructures as a function of depth with a 4-nm lateral resolutio n and a 10-nm depth resolution. (C) 1998 Elsevier Science Ltd. All rig hts reserved.