News of the Week The Atochem/ICI agreement would remove some of the competitive pressure. Too, derivatives made at Chocques would extend ICTs prod uct range, and fit in with its strate gy of moving further into morespecialized, higher-priced items. European overcapacity also exists for LDPE. The expected phaseout of ICTs 154 million lb facility at Rozenburg would be a step toward relieving the problem. Atochem's annual capacity for the polymer in France is some 781 mil lion lb. About 15 % of this is used for making ethylene-vinyl acetate copolymer. It plans to raise capacity for the copolymer 10 % or so following closure of the Rozenburg unit. The negotiations do not include ICI's remaining LDPE plant at Fos, near Marseille. The 220 million lb-ayear unit makes polymer for film and coatings. Presumably, the Commission of the European Communities will have to okay the restructuring. However, it took two years for the commission to act following a swap in 1982 between BP Chemicals and ICI of their U.K. LDPE and polyvi nyl chloride plants. D
Alberta lowers price of gas for petrochemicals Alberta Gas Ethylene (AGE), the huge ethylene producer in that west ern Canadian province, and its downstream customers figure to get a tremendous feedstock price break from a new natural gas pricing scheme that the Alberta government is putting into motion. The program is designed to overcome an anoma ly in Alberta law that has kept the natural gas price paid by AGE well above the prevailing intraprovincial market price. Described by an Alberta govern ment official as a "short-term, tran sitional program/' the plan, which became effective last week, will al low AGE, or more specifically, the company's suppliers who extract ethane from natural gas in straddle plants built on gas pipelines, to buy natural gas at prices up to 27% less than they now are paying. If this price advantage is passed on to AGE 6
November 12, 1984 C&EN
a n d its d o w n s t r e a m customers, Alberta petrochemical exports will get a much-needed boost in the fight for world market share. The Alberta border price for gas leaving the province is about $3.00 (Canadian) per thousand cubic feet. AGE pays just a little less—about $2.75—for its gas. But the intrapro vincial market price is only about $2.00. All industrial gas users in Alberta pay that price for their gas, including methanol and ammonia producers. All, that is, except AGE's ethane extractors. Because of a quirk in the law, and because the straddle plants are built on regulated pipe lines, they have to pay the higher, close-to-regulation price. The new program, which will re main in effect for 20 months (until July 1, 1986), will change that. The government intends to give the gas producers and their customers that much time to negotiate intrapro vincial market prices. In the mean time, the provincial government will provide funds to get ethane feed stock costs down from their present regulated base. And an amendment already has been introduced to change the law that caused the prob lem in the first place. If AGE's ethane price ends up reflecting the expected $2.00 gas price as expected, the savings would be tremendous. At full capacity, the company uses about 80 billion cu ft of gas per year. There could be one possible prob lem, however. Canada's trading part ners could consider Alberta's fund ing arrangement as an unfair subsi dy until truly free-market natural gas prices really are in place. D
Polysilanes show promise as photoresists Polysilane copolymers that are high ly sensitive to deep ultraviolet radi ation have been developed for even tual application as self-developing photoresists in the manufacture of silicon chips. The materials were developed by organic chemist John M. Ziegler and physical chemist Larry A. Harrah of Sandia National Laboratories, Albuquerque, N.M.
Polysilanes consist of a backbone of silicon atoms carrying organic substituents. An example of a poly silane copolymer developed by the Sandia researchers that has particu larly good properties as a photoresist is (isopropylmethyl silane/n-propylmethyl silane) n . On exposure to deep UV radiation, the material decom poses and volatilizes. A series of subsequent reactions results in noncorrosive and probably nontoxic sili cones as end products. As photoresists, the polysilane co polymers possess a number of prop erties to recommend them, Zeigler says. Conventional photoresists are carbon-based polymers. Unlike the polysilane copolymers, most must go through a developing step to remove material to obtain the cir cuit pattern desired. That involves exposure to a liquid solvent or, in the case of dry developing, to a plasma. In addition to extra steps, the developing process tends to de grade the quality of the pattern. Unlike the Sandia materials, selfdeveloping photoresists produce tox ic and corrosive end products. Ac cording to Zeigler, another factor is that none of the other self-devel oping photoresists are sensitive to deep UV radiation. Use of such short-wavelength radiation is becom ing increasingly important as chip manufacturers strive to achieve 1-μηι features. Although Zeigler believes that the polysilane copolymers will find use as single-layer photoresists, their greatest potential may be in con junction with other photoresists in bilayer lithography. Production of a finished silicon chip involves sev eral cycles of photoresist application, exposure to radiation, and etching. Once topography has been intro duced on the silicon wafer, light scattering in the exposure step can become a problem. Bilayer lithography overcomes that problem. It involves deposit ing a relatively thick layer of one photoresist to produce a flat surface and them depositing another, imag ing layer of photoresist on top of that. Zeigler says the properties of the polysilane copolymers make them an obvious choice for the imaging-layer photoresist in such a process. D
