Fishing – trapping – and vermin destroying
Patent
1993-01-26
1995-11-28
Hearn, Brian E.
Fishing, trapping, and vermin destroying
437240, 437982, 148DIG133, H01L 21469
Patent
active
054707986
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to a process for applying spin-glass to a substrate, and more particularly to a process for the planarization of semiconductor wafers. The invention is especially applicable to inorganic spin-on glasses.
2. Description of the Prior Art
Spin-on glasses (SOG) are proprietary liquid solutions containing siloxane or silicate based monomers diluted in various kinds of solvents or alcohols. They are commonly used for the planarization of semiconductor wafers, i.e. the filling and levelling of the trenches formed between interconnect paths deposited on the wafer. On coating and curing of spin-on glasses, monomers are polymerized by condensation and release of water, solvent, and alcohol. The condensed material is a thin solid film having mechanical, chemical and electrical properties which depend on the starting solution, and the coating and curing process.
There are more than one hundred different SOG solutions currently available. These are classified into two major families:
The difficulty of using silicate SOGs for the planarization of low-melting point materials, such as aluminum has caused a worldwise trend not to use purely inorganic silicate (including phosphosilicate) SOGs and to use instead members of the quasi-inorganic siloxane family.
However, there are significant disadvantages in using quasi-inorganic SOGs relating to their electric properties, and their use is becoming uncertain for advanced applications.
A further problem is caused by the absorption of water during curing. SOGs, particularly phosphorus alloyed SOGs, are extremely hygroscopic materials, and rapidly absorb ambient moisture during curing. This moisture pick-up promotes the irreversible reactions described above, and the resulting SOG films have poor properties and reliability.
SUMMARY OF THE INVENTION
An object of the invention is to alleviate the aforementioned problems by permitting the obtention of higher quality SOG films, mainly inorganic SOG films, over aluminum or other materials that cannot tolerate high temperature processing.
In accordance with the present invention the spin-on glass is an inorganic spin-on glass which is applied in the following manner: chamber in a moisture-free environment; station; been achieved without in the interim exposing the wafer to ambient conditions such that reverse hydrolysis is minimized during the planarization process.
The various components of a SOG solution (silicon containing oligomer, solvents mixture, and residual water) are in equalibrium in the liquid phase. Immediately after coating, volatile products (solvents and water) evaporate, and polymerization occurs due to the formation by condensation of silanol, Si--OH bonds. These produce more water according to the following reaction: ##STR1##
Polymerization continues until the distance between neighboring silanol groups, Si--OH, becomes too large or when too much by-product, such as water, blocks the condensation reaction. Heating is then required to permit further densification.
Both families of SOG solutions can incorporate boron or phosphorus organometallic catalyst to improve the properties of the films, such as: higher density, reduced hydrogen content, higher coefficient of thermal expansion, better flexibility and higher resistance to cracking. In the SOG solution, the boron or phosphorus organometallic molecules are generally not well bonded to the silicon-containing compounds. Strong bonding generally occurs in the solid state when the film is exposed to relatively high temperatures. These organometallic molecules can nevertheless polymerize in the solution to form poorly bonded polymers that dissociate and form stable polymers during coating and condensation of the film. As an example, a Japanese SOG solution is alloyed with a phosphorus organometallic molecule, P.sub.w O.sub.x (OH).sub.y (OC.sub.2 H.sub.5).sub.z, which is in dynamic equilibrium with the solutions water and ethanol, C.sub.2 H.sub.5 OH: ##STR2##
If the ethanol C.sub.2
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patent: 4962063 (1990-10-01), Maydan et al.
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Hearn Brian E.
Mitel Corporation
Trinh Michael
LandOfFree
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