Multi-level interconnection CMOS devices with SOG

Details Multi-level interconnection CMOS devices with SOG Multi-level interconnection CMOS devices with SOG

1993-04-30

1995-10-10

Hearn, Brian E.

Fishing, trapping, and vermin destroying

437225, 437228, H01L 21469

Patent

active

054570735

DESCRIPTION:

BRIEF SUMMARY
This invention relates generally to the fabrication of semiconductor wafers, and more particularly to a method of manufacturing a semiconductor wafer, wherein at least one high-temperature resistant water absorbant, organic or quasi-organic dielectric layer is formed between first and second layers of deposited interconnect material interconnected through vias opened in the dielectric layer.
Spin-on glass (SOG) is a proprietary liquid solution containing silicate (purely inorganic spin-on glasses) or siloxane (quasi-inorganic spin-on glasses) based monomers diluted in various kinds of solvents or alcohols. It is mainly employed as a planarizing medium in the manufacture of semiconductor wafers to fill in trenches formed during the fabrication process, which involves depositing a plurality of layers, some of which are partially etched during the fabrication process. During coating and curing, monomers are polymerized by condensation of silanol, .cndot.SiOH, and ethoxy groups, .cndot.SiOC.sub.2 H.sub.5, and release water vapour, ethanol, and other by-products according to the following scheme: ##STR1##
Polymerization of the SOG solution ceases when the distance between neighboring silanol groups, .cndot.SiOH, becomes too large or when too much by-product, such as water vapour, blocks the condensation mechanism. Heating is then needed to eliminate condensation by-products and permit further condensation, densification, and the formation of a hard inorganic or quasi-inorganic film, i.e. the SOG film.
The final density of the SOG films depends on many factors but is generally lower than the density of other inorganic or quasi-inorganic glasses deposited by other commonly used techniques like LPCVD or PECVD. This lower density is due to the presence of many pores in the SOG film, which cause high conductance channeling paths between the film surface and its bulk. These pores permit the adsorbed gas molecules present on the SOG film surface to continuously and rapidly diffuse through the bulk of the film and to rapidly connect physically to the glass by forming low energy (<0.1 eV) Van der Waals bonds (drawn as ".cndot. .cndot." in the following scheme); the gas molecules are rapidly absorbed physically by the SOG film network.
Some gases, such water vapour, have molecules that can slowly form high energy (>0.1 eV) chemical bonds (drawn as ".cndot." in the following scheme) with the SOG film network by forming a pair of silanol groups, .cndot.SiOH. Water vapour molecules are slowly chemically absorbed by the SOG film network. ##STR2##
This slow chemical absorption of water vapour by the SOG film is particularly efficient if the SOG solution contains phosphorus organometallic molecules, which give very efficient water vapour gettering due to the presence of phosphorus-oxygen double bounds in the SOG film, as shown by the following scheme: ##STR3##
This gettering of water vapour by absorption can be verified by infrared spectroscopy by monitoring the behaviour of these P:O bonds and other bonds in the presence of water vapour [see for example, R. M. Levin, J. Electrochem. Soc., Vol. 129, No. 8, pp. 1765-1770; M. Noyori and Y. Nakata, J. Electrochem. Soc., Vol. 131, No. 5, pp. 1109-1114].
As a reference, the following tables give the approximate location of the infrared absorption bands associated with the different inter-atomic vibrations of some selected bonds associated with the interaction of water vapour with phosphorus doped inorganic silicate thin films:


______________________________________ APPROX. WAVE NUMBER [cm.sup.-1 ] ______________________________________ RELATED TO "OXYGEN-HYDROGEN" VIBRATIONS in phase stretching of O--H in "H.OH" 3350 in phase stretching of O--H in "H.OSi" 3650 in phase stretching of O--H in "H.OP" 3700 RELATED TO "OXYGEN-SILICON" VIBRATIONS rocking of Si--O--Si 460 banding of Si--O--Si 810 in phase stretching of O--Si in "Si.OH" 930 in phase stretching of O--Si in "Si.OSi" 1070 in phase stretching of O--Si in "Si.OP" 1090 out of pha

REFERENCES:
patent: 4962063 (1990-10-01), Maydan et al.
L. D. Molnar, "SOG Planarization Proves Better Than Photoresist Etch Back," Aug. 1989, pp. 92-96.
Wolf et al., vol. II, Silicon Processing for the VLSI Era, Lattice Press, 1990, pp. 268-273.
H. G. Tompkins & C. Tracy, J. Electrochem. Soc., vol. 136, No. 8, pp. 2331-2335 "Desorption from Spin-On Glass".

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