Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2003-03-12
2004-07-20
Potter, Roy (Department: 2822)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S613000
Reexamination Certificate
active
06764937
ABSTRACT:
BACKGROUND
Solder is a material that typically contains tin and lead and that is commonly used during the manufacturing of electronic circuit boards. Solder generally has a lower melting temperature than the metals that may be included, as lines or layers, in the circuit boards. Hence, once two or more metal lines or layers have been formed in a circuit board, solder may be used to form an electrical contact between the layers and/or lines.
FIGS. 1A-1E
show cross-sections of semiconductor device structures after various steps of a process for depositing solder on a planar semiconductor substrate surface have been performed according to the related art.
FIG. 1A
is a cross-sectional view of a semiconductor substrate
100
, such as silicon or gallium arsenide, and of an organic film
110
, such as a photoresist film, that has been deposited on the semiconductor substrate
100
. The organic film
110
, according to the related art, is typically spun onto the substrate
100
and is typically in contact with the entire surface of the semiconductor substrate
100
.
FIG. 1B
is a cross-sectional view of the layers
100
,
110
discussed above after the organic film
110
has been selectively etched to form a series of holes
120
(or channels, troughs, grooves, or openings) above the substrate
100
. The holes
120
in the organic film
110
may be formed via photo-lithography or by any other process known in the art of semiconductor device manufacturing.
FIG. 1C
is a cross-sectional view of the substrate
100
and organic film
110
discussed above after the holes
120
in the organic film
110
have been filled, at least partially, with solder paste
130
. Solder paste, in general, typically includes an admixture of flux and solder particles. The solder paste
130
shown in
FIG. 1C
may be deposited in the holes
120
by any process known in the art. For example, a process similar to the stencil printing process used in the surface mount assembly process can be used. Specifically, a squeegee can be used to “roll” a bead of solder paste
130
across the organic film
110
to deposit the solder paste
130
into the holes
120
.
FIG. 1D
is a cross-sectional view of the substrate
100
after the solder paste
130
has been heat-treated to form solder bumps
140
on the substrate
100
. In order to form the solder bumps
140
, the temperature of the solder paste
130
that had been in the holes
120
of the organic film
110
was raised. The higher temperature caused the flux portion that had been in the paste
130
to liquefy and activate the metal surfaces and caused the solder particles in the paste to melt. In the molten phase, the solder will wet to a solderable pad on the substrate surface while the surface tension of the liquid solder will cause the molten solder to form the shape of the solder bump. Upon cooling of the melted solder particles, solid solder bumps
140
were formed. Typically, the temperature of the solder paste
130
is raised by the use of an oven or hot plate.
FIG. 1E
is a cross-sectional view of the substrate
100
and the solder bumps
140
after the organic film
110
has been removed. The organic film
110
may be removed by any process that known in the art. Upon removal of the organic film
110
, the substrate
100
may have additional structures, such as metal layers and metal lines, deposited thereon, and the solder bumps
140
can be used to electrically connect two or more metal layers or lines.
SUMMARY
A method of depositing solder, the method including the steps of providing a substrate that includes a substantially planar surface and a sloped surface adjacent to the substantially planar surface, forming a wettable layer on a portion of the sloped surface, and forming a solder layer on a first portion of the wettable layer.
A semiconductor device including a substrate having a substantially planar surface and an interior sloped surface, a wettable layer adhered to a portion of the interior sloped surface, and a solder layer adhered to a first portion of the wettable layer.
REFERENCES:
patent: 5539153 (1996-07-01), Schwiebert et al.
patent: 5736456 (1998-04-01), Akram
Berauer Frank
Vander Plas Hubert Allen
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