Resists formulations

Since the original proof of concept, and a later demonstration of its practical use in semiconductor manufacturing (40), appHcations and extensions of this concept have proliferated. In the following sections these systems are described in greater detail with emphasis on the resist formulation at a components level (41). 

A second approach modifies the CA resist chemistry. Eor example, researchers have introduced basic additives into the resist formulation to minimize the impact of surface contamination of the resist film (82,83). A resist that already contains added base (and consequendy requites a larger imaging dose) should be less affected by the absorption of small amounts of basic contaminants. Systems of this type have been claimed to have improved resolution as well. The rationalization here is that the acid that diffuses into the unexposed regions of the resist film is neutralized and does not contribute to image degradation (84,85). 

Other anhydrides that have been used include dodecenylsuccinic anhydride, which imparts flexibility into the casting, and chlorendic anhydride, where flame-resistant formulations are called for. 

Frost-Resistant Formulation for Hydraulic Fracturing Fluids [147]... 

A frost-resistant formulation from a Russian patent [147] is given in Table 17-19. The composition has a frost resistance down to —35° to —45° C. 

A corrosion-resistant formulation [1767] is achieved by adding phosphonic acid and hydrazine hydrochloride, as shown in Table 18-3. Hydrazine hydrochloride, combined with nitrilo-trimethyl phosphonic acid, provides a synergetic effect of increased inhibition of the plugging solution. 

Precision injection molding where feasible, gamma radiation resistant formulations, and improved production traceability and quality. 

The polymer TBSS is known to undergo radiation induced chain scission and provides an improvement in the sensitivity compared to resists formulated with polymers which do not undergo chain scission. The lithographic performance of a resist formulated from this polymer and 2,6-dinitrobenzyl tosylate acid generator is reported. 

In the present study we use the acid catalyzed crosslinking reaction directly (Scheme 1) as a means to estimate the amount of acid generated in a typical AHR resist. We then use the model proposed by Seligson and coworkers to determine the activation energy of crosslinking for a variety of crosslinking resins as they might be used in a resist formulation. Where... 

The response of crosslinkers 1-4 to pTSA catalysis as a function of acid concentration is shown in Figure 2 for a 75°C/1 minute softbake and 105°C/1 minute hardbake cycle. The concentration of acid required to crosslink these films to a given LP is an indication of the relative resist sensitivities, while the steepness of the LP curves reflects resist contrast. Crosslinkers 3 and 4 are about twice as sensitive to pTSA catalysis as 1, while 2 requires a higher concentration of pTSA for crosslinking. Furthermore, the steepness of the curve for 3 suggests that it would show higher contrast in a resist formulation. 

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,... 

Figure 4. SEM micrographs depicting 0.5 (im 1/s with e-beam exposure of (a) resist formulated with crosslinker 1 (6.2 iC//cm2), (b) resist formulated...

This basic approach to chemical amplification was subsequently extended by Ito et al. [3] through resist formulations incorporating appropriately chosen triaryl sulfonium or diaryliodonium salt. For example, end-capped poly(phthalaldehyde) used in combination with an onium salt photoacid generator is an excellent self-... 

The incorporation of PDMSX into conventional novolac resins has produced potential bilevel resist materials. Adequate silicon contents necessary for O2 RIE resistance can be achieved without sacrificing aqueous TMAH solubility. Positive resist formulations using an o-cresol novolac-PDMSX (510 g/mole) copolymer with a diazonaphthoquinone dissolution inhibitor have demonstrated a resolution of coded 0.5 pm L/S patterns at a dose of 156 mJ/cm2 upon deep-UV irradiation. A 1 18 O2 etching selectivity versus hard-baked photoresist allows dry pattern transfer into the bilevel structure. 

The 4-sulfonate isomers have found use in certain formulations. These materials are easily identified, since they have a single absorbance maximum in the wavelength region of interest that is centered at approximately 380 nm., and they have little or no absorbance at 436 nm (Figure 21). The absorbance spectra of two representative positive resist formulations are provided in Figures 22 and 23. These spectra were obtained by casting the resists on quartz substrates and then recording the absorbance... 

Figure 21. Absorbance spectrum of a l-oxo 2 diazonaphthoquinone-4-arylsulfonate. These materials differ spectrally from the 5 isomers shown in Figure 20 and are used in certain commercial resist formulations.

Though certain positive resist formulations that are commercially available have been shown to function satisfactorily under MUV exposure conditions in terms of the image quality that can be generated (77,72), none of these provides a throughput capability comparable to that obtainable under NUV conditions. IBM researchers have recently described the development of a resist designed specifically for exposure in the MUV spectral region (79). The resist is a two-component, positive system based on... 

Wilkins and coworkers have redesigned both the sensitizer and the matrix resin (78-79). They have tested a variety of o-nitrobenzyl esters of cholic acid as sensitizers. These substances, like the diazoquinones, are insoluble in aqueous base but undergo a photo-reaction that yields base soluble products. The matrix resin chosen for the new sensitizer materials is a copolymer of methyl methacrylate and methacrylic acid that is far more transparent than novolac resins in the DUV. The new resist materials are reported to have useful sensitivity (ca. 00mJ/cm ) and extremely high contrast. The resist formulation is essentially aliphatic in nature and would be expected to be less stable to dry etching environments than the aromatic-based novolac resin materials (24). 

Agents in this class are omeprazole, lansoprazole, pantoprazole and rabeprazole. Esomeprazole is the S-enantiomer of omeprazole. After ingestion of gastric acid resistant formulations they are rapidly and more or less completely absorbed. Bioavailability may be reduced if administered with food or antacids. Elimination is via metabolism in the liver and the renal excretion of inactive metabolites. The elimination half-live is very variable, however, as explained above, not related to the duration of action. 

A chemically amplified positive-resist formulation was prepared by mixing the following components ... 

The resist formulation was spin-coated onto a silicone wafer on which a bottom antireflective coating had been previously applied and then soft-baked for 60 seconds at 90°C on a hot plate to obtain a film thickness of 1000 nm. The resist film was then exposed to i-line radiation of 365 nm through a narrowband interference filter using a high-pressure mercury lamp and a mask aligner. Experimental samples were then baked for 60 seconds at 90°C on a hot plate and developed. The dose to clear, E0, which is the dose just sufficient to completely remove the resist film after 60 seconds immersion development in 2.38% aqueous tetramethyl ammonium hydroxide, was then determined from the measured contrast curve. Testing results are provided in Table 1. 

Smaller dosages indicate higher sensitivity in the resist formulation. 

Introduction of Conjugation The best example of imparting higher thermal stability through the introduction of conjugation in explosive molecules is hexanitrostilbene (HNS), synthesized by Shipp [58, 59] of the US Naval Ordnance Laboratory (NOL) in 1964. Plants for full-scale production exist in the UK and China, based on the method of Shipp [60]. It has proved its efficiency as a heat-resistant explosive as well as a component of heat-resistant formulations employed in the Apollo spaceship and for seismic experiments on the moon [61]. HNS has also been reported for use in achieving stage separation in space rockets. 

Although other resist systems have been described in the literature, it does not appear that these newer resist formulations will displace the older more established resists for conventional wavelengths. Much more interest is being shown in dry-developable photoresists which will be discussed later. 

The structural variations of Novolak resins also influence how well they mix or form solid solutions with a dissolution inhibitor when resist films are cast onto substrates. This is a crucial problem for resist formulation. Usually, cresol-formaldehyde Novolak resins mix well with photoactive compounds like a... 

Wahbi et al. [32] used a spectrophotometric method for the determination of omeprazole in pharmaceutical formulations. The compensation method and other chemometric methods (derivative, orthogonal function, and difference spectrophotometry) have been applied to the direct determination of omeprazole in its pharmaceutical preparations. The method has been validated the limits of detection was 3.3 x 10 2 /ig/ml. The repeatability of the method was found to be 0.3-0.5%. The linearity range is 0.5-3.5 /ig/ml. The method has been applied to the determination of omeprazole in its gastro-resistant formulation. The difference spectrophotometric (AA) method is unaffected by the presence of acid induced degradation products, and can be used as a stability-indicating assay method. 

JP 05311144 (Japanese) 1993 Heat-resistant adhesive compositions containing polyimide-siloxane block copolymers Ube Industries, Japan H Inoe, S Takabayashi, T Funakoshi, K Sonoyana Useful for Cu-clad laminates of printed circuit boards and tape-automated bonding with good flexibility and heat resistance Formulated compositions containing siloxane-imide block copolymers made from aromatic tetracarboxylic acids and aromatic diamines and aminosiloxanes... 

No new information is conveyed by using a resistance formulation, but some workers may find it convenient to think in these terms. When a numerical solution is to be performed which takes into account property variations, the resistance formulation is particularly useful. 

The resistance formulation is also useful for numerical solution of complicated three-dimensional shapes. The volume elements for the three common coordinate systems are shown in Fig. 3-11, and internal nodal resistances for each system are given in Table 3-3. The nomenclature for the (m, rt, k) subscripts is given at the top of the table, and the plus or minus sign on the resistance subscripts designates the resistance in a positive or negative direction from the central node (m, n, k). The elemental volume AV is also indicated for each... 

It is useful to think in terms of a resistance formulation for this problem because all the connecting resistances between the nodes in Fig. 3-6 are equal that is,... 

The nodal network for a typical section of the glass is shown in the figure. In this example we have not chosen Ax = Ay. Because of symmetry, T = TV, T2 = Tt, etc., and we only need to solve for the temperatures of 16 nodes. We employ the resistance formulation. As shown, we have chosen Ax = 5 mm and Ay = 1 mm. The various resistances may now be calculated ... 

For this example we choose nonsquare nodes as shown. Note also that nodes I, 4, 7, 10, 13, 14, and 15 consist of two materials. We again employ the resistance formulation. 

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