Texas Instruments Corporation

Gregory P Johnston

Douglas M Smith

Shin-Puu Jeng

William C Ackerman

Bruce E Gnade

Richard A Stoltz

Teresa A Ramos

Alok Maskara

This invention has enabled a new, simple thin film nanoporous dielectric fabrication method. In general, this invention uses glycerol, or another low volatility compound, as a solvent. This new method allows thin film aerogels/low density xerogels to be made without supercritical drying, freeze drying, or a surface modification step before drying. Thus, this invention allows production of nanoporous dielectrics at room temperature and atmospheric pressure, without a separate surface modification step. Although this new method allows fabrication of aerogels without substantial pore collapse during drying, there may be some permanent shrinkage during aging and/or drying. This invention allows controlled porosity thin film nanoporous aerogels to be deposited, gelled, aged, and dried without atmospheric controls. In another aspect, this invention allows controlled porosity thin film nanoporous aerogels to be deposited, gelled, rapidly aged at an elevated temperature, and dried with only passive atmospheric controls, such as limiting the volume of the aging chamber.

Low volatility solvent-based method for forming thin film nanoporous aerogels on semiconductor substrates

This invention pertains generally to precursors and deposition methods suited to aerogel thin film fabrication. An aerogel precursor sol which contains an oligomerized metal alkoxide (such as TEOS), a high vapor pressure solvent (such as ethanol) and a low vapor pressure solvent (such as water and 1-butanol) is disclosed. By a method according to the present invention, such a precursor sol is applied as a thin film to a semiconductor wafer, and the high vapor pressure solvent is allowed to evaporate while evaporation of the low vapor pressure solvent is limited, preferably by controlling the atmosphere adjacent to the wafer. The reduced sol is then allowed to gel at a concentration determined by the ratio of metal alkoxide to low vapor pressure solvent. One advantage of the present invention is that it provides a stable, spinnable sol for setting film thickness and providing good planarity and gap fill for patterned wafers. In addition, however, the reduced sol may be gelled rapidly from a known sol concentration keyed to the desired final density of the aerogel thin film and largely independent of film thickness and spin conditions.

Aerogel thin film formation from multi-solvent systems

This pertains generally to precursors and deposition methods suited to aerogel thin film fabrication of nanoporous dielectrics. An aerogel precursor sol is disclosed. This aerogel precursor sol contains a metal alkoxide (such as TEOS) and a solvent, but no gelation catalyst. By a method according to the present invention, such a precursor sol is applied as a nongelling thin film,to a semiconductor substrate,This substrate may contain patterned conductors,gaps,or other structures. An independent gelation catalyst (preferably, vapor phase ammonia) is added to promote rapid gelation of the thin film sol,at the desired time. One advantage is that it allows substantially independent control of gelation and pore fluid evaporation. This independent catalyst introduction allows additional processing steps to be performed between sol deposition and the onset of substantial gelation. One potential step is to evaporate a portion of the pore fluid solvent. Additional advantages of independent catalyst introduction are that it reduces the need for process steps requiring critical timing and provides a large increase in the pot life of the precursor sol.

Nanoporous dielectric thin film formation using a post-deposition catalyst

This invention pertains generally to precursors and deposition methods suited to aerogel thin film fabrication. An aerogel precursor sol which contains an oligomerized metal alkoxide (such as TEOS), a high vapor pressure solvent (such as ethanol) and a low vapor pressure solvent (such as water and 1-butanol) is disclosed. By a method according to the present invention, such a precursor sol is applied as a thin film to a semiconductor wafer, and the high vapor pressure solvent is allowed to evaporate while evaporation of the low vapor pressure solvent is limited, preferably by controlling the atmosphere adjacent to the wafer. The reduced sol is then allowed to gel at a concentration determined by the ratio of metal.alkoxide to low vapor pressure solvent. One advantage of the present invention is that it provides a stable, spinnable sol for setting film thickness and providing good planarity and gap fill for patterned wafers. In addition, however, the reduced sol may be gelled rapidly from a known sol concentration keyed to the desired final density of the aerogel thin film and largely independent of film thickness and spin conditions.

This pertains generally to precursors and deposition methods suited to aerogel thin film fabrication of nanoporous dielectrics. A method of forming a nanoporous dielectric on a semiconductor substrate is disclosed. By a method according to the present invention, a precursor sol is applied as a nongelling thin film 14 to a semiconductor substrate 10. This substrate may contain patterned conductors 12, gaps 13, and/or other structures. A portion of the solvent is evaporated from the thin film 14 to produce a reduced thickness film 18. Film 18 is gelled and may be aged. A surface modification agent is introduced to the reaction atmosphere in a vaporish form, e.g., a vapor, mist, aerosol, or similar form. The surface modifier can then diffuse into, condense onto, and/or settle onto the wet gel and then diffuse throughout the thin film. This vaporish introduction of the surface modification agent ensures that there are no strong fluid flows across the wafer that might damage the wet gel. It can also be compatible with standard processing equipment and can potentially be used with other reaction atmosphere controls that reduce premature drying of the gel.

Nanoporous dielectric thin film surface modification

Low volatility solvent-based method for forming thin film nanoporous

This invention pertains generally to aging methods suited to aerogel thin film fabrication, and particularly to techniques for improving gel strength and/or aerogel dielectric constant by a rapid aging technique, which avoid damage or premature drying of wet gel thin films during aging. A substrate having a wet gel thin film deposited thereon is contacted with a saturated water vapor atmosphere, preferably at an elevated pressure and a temperature greater than 100.degree. C. The method may comprise a vapor-phase exchange step to remove low boiling point pore liquids such as ethanol prior to or during aging. The method may also comprise a vapor-phase exchange step to replace water in the wet gel with another pore liquid such as acetone to stop the aging process and prepare the wet gel for drying. A vapor-phase aging catalyst (e.g. ammonia) may also be used to enhance the aging process. The present invention allows aging of wet gel thin films to be completed in a few minutes instead of the days generally required for conventional bulk gel aging.

Growing community of inventors

Albuquerque, NM, United States of America

Gregory P Johnston