Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2002-01-03
2003-11-04
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S790000, C134S031000, C134S033000
Reexamination Certificate
active
06642142
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a substrate cleaning method and method for producing an electronic device that uses this cleaning method. In particular, the present invention relates to a method in which the formation of a recess by performing dry-etching for an insulating film is followed by the removal of residue from the side walls or bottom of the recess using a cleaning solution and then by a short, efficient rinsing of the recess with water.
When producing electronic devices, dry etching techniques are commonly used to pattern an insulating film or conductive film, for example. When doing so, a known problem is that residue (such as side wall protection film and remaining polymer) that is caused by an etching gas, a photoresist or a processed film is often left around the etched pattern (such as the via holes and wires), formed by the dry etching. If such residue is left in the via holes, for example, problems can result, such as poor connections between the upper and lower wiring layers and increased resistance of the via holes. Also, if residue is present on the side walls of wiring, for example, this can cause short circuits between adjacent wires. In this way, the presence of such residue can drastically reduce the reliability of an electronic device.
In order to remove such residue, it is now common practice to use a cleaning solution that includes various organic or inorganic compounds. Also, in the cleaning process that uses this kind of cleaning solution, or in the rinsing process with water that follows the cleaning process, the cleaning or rinsing can be made more thorough by using a single-wafer-processing-type or batch-processing-type spin cleaner.
FIG. 6
shows how the surface of a processed substrate (a substrate to be processed is also referred to as “processed substrate” in this specification) composed of a semiconductor wafer is rinsed with water using a single-wafer-processing-type spin cleaner.
As shown in
FIG. 6
, a single-wafer-processing-type spin cleaner supports a single processed substrate
60
with a spin chuck (not shown) that is fixed to the rotation shaft of a motor
61
. While the motor
61
is rotating the processed substrate
60
, the nozzle
62
expels water
63
onto the processed substrate
60
so as to rinse the surface of the processed substrate
60
with water.
FIG. 7
shows how the surfaces of processed substrates composed of semiconductor wafers are rinsed with water using a batch-processing-type spin cleaner.
As shown in
FIG. 7
, a batch-processing-type spin cleaner supports a plurality of processed substrates
70
with a rotor
72
that is fixed to the rotation shaft of a motor
71
. While the motor
71
is rotating the processed substrates
70
, the nozzles
73
expel water
74
onto the processed substrates
70
so as to rinse the surfaces of the processed substrates
70
with water.
In recent years, the scale down and improved packing ratio of electronic devices has led to a reduction in the dimensions of etching patterns, such as in the diameter of the via holes. As a result, when a cleaning process that uses a cleaning solution is followed by a water rinsing process, there is a reduction in the efficiency with which the cleaning solution is replaced with water in the via holes, especially near the bottoms of the via holes. This occurs even when a spin cleaner is used. Near the bottoms of the via holes, there is a decrease in the speed of dispersion of the cleaning solution, so that more time is required to perform the water rinsing process. Depending on the type of cleaning solution used, cleaning solution that has been diluted with water can cause corrosion of the conductive film or the like. This means that as the water rinsing process becomes longer, there is a concurrent increase in the length of time the areas around the bottoms of the via holes provided on top of the wiring, for example, are exposed to diluted cleaning solution. This can cause corrosion of the wiring and a fall in the reliability of electronic devices produced in this way.
SUMMARY OF THE INVENTION
In view of the above, it is an object of the present invention to shorten the time required by a water rinsing process, which is performed after a processed substrate has been cleaned using a cleaning solution, by raising the efficiency with which the cleaning solution is replaced with water.
In order to achieve the above object, as a comparative example, the inventors first tried rinsing via holes formed in an insulating film on a substrate with water using a spin cleaner after using a cleaning solution to remove residue from the side walls and other parts of the via holes. Note that in this comparative example, a cleaning solution formed by adding a fluorine compound, which is capable of etching the insulating film, to an organic solvent is used as the cleaning solution for removing residue. Hereafter, such cleaning solution is referred to as a “fluorine-containing cleaning solution”. As examples, the fluorine-containing cleaning solutions disclosed in Japanese Laid-Open Patent Applications H07-201794 and H10-55993 were used. When using such a fluorine-containing cleaning solution, there is no risk of the insulating film being excessively etched, which would result in the via holes being badly deformed. However, when a fluorine-containing cleaning solution is diluted with water, the fluorine compound in the cleaning solution ends up having an etching effect for the conductive film, resulting in corrosion of the conductive film.
FIG. 8
shows one example of the relationship between the dilution factor of the fluorine-containing cleaning solution and the etching rate of the conductive film by the fluorine-containing cleaning solution. As shown in
FIG. 8
, the fluorine-containing cleaning solution exerts a strong etching effect for the conductive film when the dilution factor with water is within in a specified range.
FIGS. 9A
to
9
C are cross-sectional diagrams showing the processes in a method for producing an electronic device according to this comparative example.
First, as shown in
FIG. 9A
, wiring
84
that is composed of a laminated structure of a first titanium nitride film
81
, an aluminum alloy film
82
, and a second titanium nitride film
83
is formed on a substrate
80
composed of a semiconductor wafer. After this, an insulating film
85
is formed on top of the wiring
84
. Next, a resist film is formed on the insulating film
85
, and the resist film is exposed to light in a desired pattern using a conventional projection method. By developing the resist film that have been exposed using a conventional developing process, a resist pattern
86
is formed with openings at areas where via holes are to be formed.
Next, dry etching is successively performed for the insulating film
85
and the second titanium nitride film
83
with the resist pattern
86
as a mask. As shown in
FIG. 9B
, once via holes
87
have been formed, plasma ashing is performed to remove the resist pattern
86
. When doing so, residue
88
ends up on the side walls and in the bottom of the via holes
87
.
As shown in
FIG. 9C
, a single-wafer-processing-type or batch-processing-type spin cleaner (not shown) is used to remove the residue
88
. This apparatus supplies a fluorine-containing cleaning solution at 23° C. for 5 to 10 minutes to the surface of the substrate
80
while rotating the substrate
80
at a predetermined rotation speed in a range (called the “low rotation region”) of 10 to 200 rpm (revolution per minute), for example. The same spin cleaner is then used to rotate the substrate
80
at a predetermined rotation speed in the low rotation region while rinsing the surface of the substrate
80
including the via holes
87
with water. The substrate
80
is then dried. If the openings of the via holes
87
are small, during the water rinsing process that follows the cleaning process that uses the fluorine-containing cleaning solution, there is a drop in the efficiency with which the fluorine-containing cleaning solution is re
Asaoka Yasuhiro
Muranaka Seiji
Nagai Toshihiko
Tanaka Hiroshi
Yokoi Naoki
Luk Olivia
Matsushita Electric - Industrial Co., Ltd.
Niebling John F.
Nixon & Peabody LLP
Studebaker Donald R.
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