Top surface imaging resists

Typical vapor phase silylating agents used in top surfaee imaging systems include dimethylsilyldimethylamine (DMSDMA), trimethylsilyldimethylamine (TMSDMA), and trimethylsilyldiethylamine (TMSDEA). Typical liquid phase silylating agents used in top surfaee imaging systems inelude 1,1,33,5,5-hexamethylcyclotrisilazane and bis(dimethylamino)dimethylsilane with N-methyl-2- pyrrolidone (NMP) as a diffusion promoter. Typical polymer resins include polyvinyl phenol and novolac/diazoquinone polymer resins. 

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The three main approaches to multilayer resist imaging systems (see Chapter 16 for details) include (i) hard mask (HM) processes, (ii) top surface imaging (TSI) processes requiring latent image formation only near the surface of the resist, thus circumventing any transparency requirements, and (iii) bilayer resist (BLR)... 

In contrast to the si tion processes in i ch the near-surface region is modified, far fewer aiq>roadies exist for direct man ulation of the top oaf ace of a substrate to provide high resolution patterns of etch resistant materials. The initial report of top-surface imaging (TSfi utilized selective deposition of TIOj on the photo-oxidized surface of hydrophobic pofymers (4, 5). 

In the deep UV region, exposure tools which use the conventional Hg lamps require fast resists (< 15 mj/cm ) in order to provide short exposure times and sufficient throughput. To meet the photospeed requirements, resists based on the incorporation of TBOC groufis onto the PHOST backbone pioneered the era of acid catalyzed amplified tems. Both negative, positive, and top surface imaging (TSI) resists based on TBOC have been formulated for the deep UV region (3, 5). 

The Perkin Elmer projection printer is the tool most currently used in photolithography manufacturing. Because of the interference of photons at the resist-substrate interface and the absorption of the resist, it is always more difficult to develop the bottom of the resist image to size than to obtain a surface image. A double layer technique has been developed to resolve this problem. The top image layer is sensitized DQ and the bottom layer is composed of a DQ derivative. 

Figure 4. Typical top surface (left) and sidewall (right) images of Shipley SAL 605 negative-tone, chemically-amplified resist. The color bar at the left is representative of the peak-to-peak height difference in the images.

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