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New Product: New selective nitride etch process from FSI reduces ultra-thin oxide damage |
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Nov 20, 2006 at 05:26 PM |
 Product Briefing Outline: FSI International has introduced a new selective nitride etch process that suppresses oxide and silicon attack without generating high particle counts using its ‘MAGELLAN' Immersion Cleaning System. These applications were developed on customer wafers as part of a 45nm advanced technology program and would also be useful for older technology generations, according to the company.
Problem: While IC manufacturers continue to add new elements and materials for the production of advanced devices, they are also increasing the use of standard materials such as silicon nitride. The development of low-temperature silicon nitride deposition processes has opened the way for adding more nitride layers to the manufacturing process to solve other integration problems such as strained channel engineering and source/drain engineering. While some of these silicon nitride films are intended to remain in place on the finished device, many of them need to be removed after serving their purpose as a hard mask for etching or as an ion implantation spacer. Traditionally, silicon nitride films have been removed with boiling phosphoric acid. Traditional approaches have adequate selectivity when removing the silicon nitride in the presence of thermally grown silicon oxide and/or thick (>100 Å) deposited oxide and no exposed silicon, such as for pad nitride removal. However, newer uses of silicon nitride require selective removal in the presence of very thin chemical or native oxide and thinner deposited oxide, with no allowance for material loss. For these new applications, improved control of the hot phosphoric bath and new integration schemes - which eliminate loss of thin oxide layers - have been developed. IC makers are also faced with making a decision between high selectivity and low particle counts when etching nitride films.
Solution: FSI's new selective nitride etch processes allow IC makers to achieve high selectivity while maintaining low particle counts, according to the company. Proprietary pretreatment steps are used to suppress native oxide loss and silicon attack during nitride etch with hot phosphoric acid. Normally, hot phosphoric acid will quickly etch away the native oxide exposing the underlying silicon to attack. Pretreatment sufficiently reduces the etch rate of the native oxide to permit phosphoric acid treatments up to 15 minutes in duration without breaking through the native oxide layer. The pretreatment does not affect nitride removal rates. Particulate contamination can be an issue with nitride etch processes. Traditionally, engineers have been faced with a trade-off between nitride/oxide selectivity and particle contamination. The trade-off is controlled by the silica concentration in the bath. Higher levels of silica provide greater selectivity but also generate higher particle levels. The ‘MAGELLAN' system utilizes a new rinse process that maintains low particulate contamination even at high silica concentration.
Applications: Silicon nitride selective etch processes including, Pad, Spacer, Liner, NMOS-channel, Post low-k, Pre low-k, Pre High-k and Soft mask.
Platform: The MAGELLAN system is a 200/300mm bridge tool. FSI's proprietary surface tension gradient ‘STG' rinse/dry, ‘SymFlow' etch and ‘MegaLens'
megasonic particle removal technologies are incorporated into the platform.
Availability: November 2006 onwards.
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Product Briefings 
