Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
1998-04-30
2001-05-22
Wilczewski, Mary (Department: 2822)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C528S031000, C438S118000
Reexamination Certificate
active
06235862
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an adhesive silicone sheet, to a method for the preparation thereof, and to semiconductor devices. More particularly, this invention relates to an adhesive silicone sheet that enroute to its complete cure is inhibited from releasing low-viscosity silicone oil, that provides an excellent bond between a semiconductor chip and the corresponding attachment site, and that as a consequence of these features supports the fabrication of highly reliable semiconductor devices. The invention also relates to a very efficient method for producing this adhesive silicone sheet which yields an adhesive silicone sheet that exhibits a particularly good adhesiveness and that supports the fabrication of highly reliable semiconductor devices. The invention further relates to highly reliable semiconductor devices in which the semiconductor chip has been bonded to its attachment site using the subject adhesive silicone sheet.
BACKGROUND OF THE INVENTION
The silicone adhesives heretofore used to bond semiconductor chips to chip attachment sites have ranged from liquid curable silicone compositions to paste-like curable silicone compositions. These silicone adhesives have taken the form of curable silicone compositions comprising at a minimum an organopolysiloxane having at least 2 silicon-bonded alkenyl groups in each molecule, an organopolysiloxane having at least 2 silicon-bonded hydrogen atoms in each molecule, and a hydrosilylation reaction catalyst. Curable silicone compositions have also been used that additionally contain an adhesion promoter in the form of an organopolysiloxane containing in each molecule at least 1 silicon-bonded alkoxy group and at least 1 silicon-bonded alkenyl group or at least 1 silicon-bonded hydrogen atom (Japanese Patent Application Laid Open (Kokai or Unexamined) Number Hei 3-157474 (157,474/1991)).
However, low-viscosity silicone oil outmigrates from these curable silicone compositions during the time interval leading up to their complete cure, which has caused contamination of the environment surrounding the composition. This low-viscosity silicone oil—because it consists of low degree of polymerization (DP) organopolysiloxane present in the organopolysiloxane base component and/or low DP organopolysiloxane present in the organopolysiloxane added as adhesion promoter—has proven extremely difficult to completely eliminate. As a result, the use of these curable silicone compositions to bond a semiconductor chip to the chip attachment site has resulted in such problems as a reduced wire bondability (joinability) between the bonding pads on the chip and bonding wires or beam leads and a degradation in the reliability of the resulting semiconductor device.
SUMMARY OF THE INVENTION
The present inventors achieved the present invention as a result of extensive research directed to solving the problems described above.
In more specific terms, an object of the present invention is to provide an adhesive silicone sheet that enroute to its complete cure is inhibited from releasing low-viscosity silicone oil, that provides an excellent bond between a semiconductor chip and the corresponding attachment site, and that as a consequence of these features supports the fabrication of highly reliable semiconductor devices. Another object of the present invention is to provide a very efficient method for producing this adhesive silicone sheet which yields an adhesive silicone sheet that exhibits a particularly good adhesiveness and that supports the fabrication of highly reliable semiconductor devices. Yet another object of the present invention is to provide highly reliable semiconductor devices in which the semiconductor chip has been bonded to its attachment site using the subject adhesive silicone sheet.
The adhesive silicone sheet according to the present invention, which is intended for bonding semiconductor chips to their attachment sites, is characterized in that at least the surfaces of the sheet that will contact the chip and chip attachment site are the semi-cured product of a curable silicone composition.
The method according to the present invention for preparing the adhesive silicone sheet for bonding a semiconductor chip to the chip attachment site relates to the preparation of the adhesive silicone sheet by curing a curable silicone composition into a semi-cured state while the composition lies between substrates that are releasable with respect to the semi-cured product of said composition. The method according to the present invention is characterized in that the dielectric constant of at least 1 of said substrates is larger than the dielectric constant of said semi-cured product.
Semiconductor devices according to the present invention are characterized in that the semiconductor chip has been bonded to the chip attachment site using adhesive silicone sheet in which the semi-cured product of a curable silicone composition makes up at least the surfaces of the sheet that contacts the semiconductor chip and chip attachment site.
REFERENCES:
patent: 5145931 (1992-09-01), Nakayoshi et al.
patent: 5358983 (1994-10-01), Morita
patent: 5360858 (1994-11-01), Fujiki et al.
patent: 5438094 (1995-08-01), Fujiki et al.
patent: 5536803 (1996-07-01), Fujiki et al.
patent: 5962601 (1999-10-01), Hiroji et al.
patent: 5969023 (1999-10-01), Enami et al.
patent: 6010646 (2000-01-01), Schleifstein
Isshiki Minoru
Mine Katsutoshi
Otani Yoshiko
Yamakawa Kimio
Dow Corning Toray Silicone Co. Ltd.
Milco Larry A.
Park James
Wilczewski Mary
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