Lithographic characteristics

Lithographic Characteristics. Based on the potential of crosslinker 3 to show high sensitivity and contrast and wide process latitude, it was of interest to evaluate its lithographic capability, using crosslinker 1 as the standard for comparison. Crosslinkers 1 and 3 (equal weight) were each incorporated into otherwise identical experimental AHR resist formulations. E-beam exposures were performed so that differences in DUV absorbance characteristics of the crosslinkers could be ignored. The e-beam sensitivities of the resists containing crosslinkers 1 and 3 were 6.2 and 4.2 (lC/cm2,... 

Table VI summarizes the lithographic characteristics of PCMS, CMS, aM-CMS, chlorinated PMS and P-p-MS for polymers with comparable molecular weight and chlorine content. Chlorinated PMS and P-p-MS are as sensitive as PCMS but exhibit better contrast, especially chlorinated P-p-MS. Only the chloromethylated poly-a-methylstyrene shows similar contrast but has much lower sensitivity.

Lithographic Characteristics. The exposure response curves for P(SI-CMS) and Sl-novolac containing PMPS (SI-NPR) are shown in Figure 4, and their lithographic characteristics are summarized in... 

Table III. The sensitivities are 2 pC/cm (D ) and 8 pC/cm for P(SI-CMS) and SI-NPR, respectively. In the case of SI-NPR, PMPS affords radiation sensitivity via spontaneous unzipping after exposure (17). The mechanism is equivalent to that of NPR and the lithographic characteristics are quite similar. No evidence of incompatibility was observed.

Multi-level systems(l) allow the planarization of substrate topography formation of high aspect ratio patterns, and better resolution than single level resists. There is a drawback to such systems, however, and that is additional process complexity. To reduce this complexity, two-level resist systems have been reported(2). The top imaging layer in two-level resist systems must exibit Op-RIE resistance as well as desirable lithographic characteristics. 

Babich ED, Paraszcak J, Hatzakis M et al. (1989) A comparison of the E-beam sensitivities and relative 02-plasma stabilities of otganosilicon polymers. Part 111. Lithographic characteristics of poly-1,1,3-trimethyl-l-sila- and poly-1,1,3,3-tetramethyl-l,3-disilacyclobutenes and related silmethylene polymers. Microelectronic Eng 9 537-542... 

Figure 3 shows the sensitivity curves for SPP (solid lines) compared with that of a novolac-based resist (dashed line). From these curves, we obtained the maximum clearing dose (Dq), the dose for 50% thickness remaining (D50), and lithographic contrast (7-value). These resist characteristics are summarized in Table I. 

In this paper, the material characteristics and lithographic evaluation of this new resist are demonstrated. The resist meets the requirements for KrF excimer laser lithography, which exhibits high sensitivity, high resolution and high aspect ratio pattern profiles. 

Fig. 1. The lithographic process. A substrate is coated with a photosensitive polymer film called a resist. A mask with transparent and opaque areas directs radiation to preselected regions of the resist film. Depending on resist characteristics, exposed or unexposed portions of the film are removed using a developer solvent. The resulting pattern is then transferred to the substrate surface and the resist is stripped.

The surface characteristics of reworked substrates and several rework processes are described later in several tables and the discussion. The substrate condition following the rework process is characterized by the results of three tests ESCA or XPS [19] surface chemical composition spectra, actual lithographic resist pattern lift testing [2, 6], and water droplet contact angle measurement, 0HjO [3]. 

To accommodate the diverse needs of lithographic processes and device design specifications, resist properties vary. However, a few primary characteristics common to all resists can be used to gauge their performance. These characteristics include sensitivity, contrast, resolution, and etching resistance. Because resist performance is strongly operation dependent, comparison between materials must be made under identical conditions. 

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