Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1998-11-16
2001-04-17
Booth, Richard (Department: 2812)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
Reexamination Certificate
active
06218281
ABSTRACT:
This application is based on Japanese Patent Application No. 9-361140, filed on Dec. 26, 1997, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
a) Field of the Invention
The present invention relates to a semiconductor device and its manufacture method, and more particularly to a semiconductor device having bump electrodes suitable for flip chip bonding and its manufacture method.
With advancement of high integration and multi-function of a semiconductor integrated circuit, the number of connection electrodes of the circuit to an external circuit is increasing. Requirements for compact devices make device assembly use flip chip bonding using bump electrodes.
b) Description of the Related Art
A conventional method of forming bump electrodes will be described with reference to
FIGS. 11A and 11B
.
As shown in
FIG. 11A
, on the surface of a semiconductor substrate
200
, an insulating film
201
is formed, and a pad
202
made of aluminum (Al) is formed in a partial surface area of the insulating film
201
. The other surface area of the insulating film
201
is covered with an insulating film
203
. A metal film
204
is formed on the pad
202
and insulating film
203
, covering the whole surface of the substrate.
A photoresist film
205
having a thickness of several microns is coated on the metal film
204
. An opening
205
a
is formed through the photoresist film
205
in an area corresponding to the pad
202
. On the surface of the metal film
204
exposed at the bottom of the opening
205
a,
a bump material
206
made of SnPb alloy is deposited through electrolysis plating. The bump material
206
fills the inside of the opening
205
a,
extends thereafter from the periphery of the opening
205
a
to the surface area of the photoresist film
205
, and shows a mushroom shape.
The photoresist film
205
is thereafter removed and a portion of the metal film
204
not covered with the bump material
206
is etched and removed.
As shown in
FIG. 11B
, a reflow process is performed by heating the substrate so that the bump material of the mushroom shape changes to generally a sphere shape. In the above manner, the bump electrode
206
is formed on the pad
202
.
With the conventional method described above, when the bump material is deposited through plating, the bump material
206
takes the mushroom shape expanding around the pad
202
as shown in FIG.
11
. Therefore, if the pitch between pads becomes small, adjacent bump electrodes are likely to contact each other. It is difficult to arrange uniformly for the height of bump electrodes
206
having generally the sphere shape shown in FIG.
11
B.
Although a method of forming a solder ball on a pad through a transfer process is known, also this method is difficult to deal with a fine pitch between pads.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a semiconductor device with bump electrodes with a fine pitch and its manufacture method.
According to one aspect of the present invention, there is provided a method of manufacturing a semiconductor device comprising the steps of: preparing a semiconductor substrate having a principal surface, an exposed pad made of conductive material being formed in a partial area of the principal surface, and the other area of the principal surface being covered with a first insulating film; forming a base conductive film on the first insulating film and the pad; forming a photoresist film on the base conductive film by coating photoresist source liquid having a viscosity of 3000 to 4000 cps on the base conductive film, the photoresist film having a thickness of 50 &mgr;m or thicker and made of material having a transmittivity of 90% or higher relative to an ultraviolet ray having a wavelength of 436 nm when the photoresist film has a thickness of 200 &mgr;m; forming an opening through the photoresist film in an area corresponding to the pad to expose a partial surface area of the base conductive film; depositing a conductive bump electrode on the base conductive film exposed on a bottom of the opening; and removing the photoresist film.
Since the photoresist film has a thickness of 50 &mgr;m, it is possible to deposit the bump electrode in the opening formed through the photoresist and form a bump electrode having a height of about 50 &mgr;m. Since the bump electrode not protruding above the opening, the bump electrodes can be formed with good reproductivity on pads disposed at a fine pitch therebetween.
According to another aspect of the present invention, there is provided a method of manufacturing a semiconductor device comprising the steps of: preparing a semiconductor substrate having a principal surface, an exposed pad made of conductive material being formed in a partial area of the principal surface, and the other area of the principal surface being covered with a first insulating film; forming a base conductive film on the first insulating film and the pad; forming a photoresist film on the base conductive film; forming an opening through the photoresist film in an area corresponding to the pad to expose a partial surface area of the base conductive film; immersing the semiconductor substrate into electrolysis plating liquid and depositing a conductive bump electrode by electrolysis-plating a surface of the base conductive film exposed on the bottom of the opening while a current density is increased more the greater a height of the deposited bump electrode becomes; and removing the photoresist film.
If the aspect ratio of the opening is high, it is difficult to transport metal ions to be plated to the bottom of the opening. It is therefore preferable to set a current density smaller and a plating speed lower. As the plating progresses and the opening becomes shallow, metal ions become easy to be transported to the bottom of the opening, so that the current density can be increased and the plating speed can be increased.
According to another aspect of the present invention, there is provided a method of manufacturing a semiconductor device comprising the steps of: preparing a semiconductor substrate having a principal surface, an exposed pad made of conductive material being formed in a partial area of the principal surface, and the other area of the principal surface being covered with a first insulating film; forming a base conductive film on the first insulating film and the pad; forming a photoresist film on the base conductive film; selectively exposing and developing the photoresist film to form an opening through the photoresist film in an area corresponding to the pad to expose a partial surface of the base conductive film, the opening forming step repetitively executing a first subsidiary step and a second subsidiary step during developing the photoresist film, the first subsidiary step developing the photoresist film by applying developing liquid to the photoresist film while the semiconductor substrate is rotated, and the second subsidiary step removing thereafter photoresist swelled by the developing liquid by rotating the semiconductor substrate at a higher speed; depositing a conductive bump electrode on the partial surface of the base conductive dump exposed on a bottom of the opening; and removing the photoresist film.
If the photoresist film is thick and the aspect ratio of an opening to be developed is high, then photoresist swelled by the developing fluid becomes likely to be left on the bottom of the opening where the development progressed. By increasing the rotation speed of the substrate after the development, left photoresist can be removed, and the development can be resumed.
According to another aspect of the present invention, there is provided a method of manufacturing a semiconductor device comprising the steps of: preparing a semiconductor substrate having a principal surface, an exposed pad made of conductive material being formed in a partial area of the principal surface, and the other area of the principal surface being covered with a first insulating film; forming a base c
Fujimori Joji
Kado Kenichi
Kodama Kunio
Makino Yutaka
Matsuki Hirohisa
Armstrong Westerman Hattori McLeland & Naughton LLP
Booth Richard
Fujitsu Limited
Jones Josetta I.
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