Polymers lithographic properties

Polymer molecular properties such as molecular weight and polydispersivity have a significant effect on the lithographic behavior of the single component negative resists described above. For example, it has been shown for a series of... 

There are several problems encountered with silicon containing polymers that affect their lithographic properties. First, a decrease in Tg often accompanies silicon incorporation into a polymer. This may lead to dimensional instability of features during processing. Also, the hydrophobic nature of most useful silicon substituents may hinder the aqueous development of these resists. Careful selection of the polymer components can alleviate and/or eliminate these problems. 

Numerous studies have probed how novolac microstructure influences resist lithographic properties. In one example, a series of resists were formulated from novolacs prepared with varying feed ratios ofpara-l/neta-ctesol. These researchers found that the dissolution rate decreased, and the resist contrast increased, as the para-/tneta-cresol feed ratio increased (33). Condensation can only occur at the ortho position ofpara-o.resol, but can occur at both the ortho- and ra-positions of meta-cresol. It is believed that increased steric factors and chain rigidity that accompany increasedpara-ctescA content modify the polymer solubility. 

The development and implementation of new resists for microlithography require considerable engineering development, and chemical engineering is central to that development. Many polymer systems have lithographic properties that appear to be useful for each of the lithographic options [12],... 

We have successfully employed the trimethylsilylmethyl appendage to effect oxygen RIE resistance in both positive and negative acting electron-beam resist systems (10,11). The relatively compact nature of this substituent allows the preparation of glassy polymers useful for lithographic applications. The preparation and characterization of select trimethylsilylmethyl substituted resists will be presented in addition to a study of their radiation chemistry and lithographic properties. 

Table 3.1 summarizes the lithographic properties of methacrylate polymers 54). These polymethacrylates all exhibit similar UV absorptions with optical densities of 0.27-0.47 xm" at 215 nm, which is considerably less than that of AZ1350J in the near-UV region (0.87 jim at 405 nm). This low absorption represents ineflScient use of flux and is one reason for the low sensitivity of the system. 

The third approach employs modifications of the polymer s physical properties and/or resist processing to minimize contaminant absorption, and is described in the section, "Polymer Properties and Lithographic Performance". 

Polymer Properties and Lithographic Performance in Chemically Amplified Resins. 

TABLE 1. Physical Properties of Selected Step 5 Polymers Used as Resist Materials in Lithographic Applications 1... 

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