Metallization process for manufacturing semiconductor devices

Details Metallization process for manufacturing semiconductor devices Metallization process for manufacturing semiconductor devices

1999-08-31

2002-01-01

Nelms, David (Department: 2818)

Semiconductor device manufacturing: process

Chemical etching

C438S704000, C438S710000

Reexamination Certificate

active

06335284

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a metallization process for manufacturing semiconductor devices and a system used in the same and, more particularly, to a metal pattern formation process that minimizes corrosion failures in aluminum pattern.
2. Description of the Related Art
A metal pattern formation process for manufacturing semiconductor devices provides electrical interconnection between the devices formed on a semiconductor substrate. The process is carried out by forming a metal material layer on a certain layer over the semiconductor substrate, coating the metal material layer with photoresist, exposing and developing the photoresist according to a predetermined pattern so as to form a photoresist pattern, etching the metal material layer using the photoresist pattern as an etch mask, and removing the photoresist pattern to form a desired metal pattern.
FIG. 1
schematically shows a conventional multichamber-type dry etching system, in which a series of processes, such as etching the metal material layer and removing the photoresist pattern, are carried out. The etching system shown in
FIG. 1
is a product of AMT (Applied Materials Technology) Company (Model Name: Centura).
Referring to
FIG. 1
, the multichamber-type dry etching system comprises a transfer module
12
at its center and a plurality of processing chambers surrounding the transfer module
12
. The transfer module
12
has a robot
14
for wafer transfer therein and maintains a constant level of vacuum by a pump (not shown). Each processing chamber is connected to the transfer module
12
via a slit valve
19
. The chambers are: load lock chambers
10
a
,
10
b
serving as a stand-by area for the wafers before/after a process, a flat-zone aligner
20
for aligning the flat-zone of the wafer for a process, etching chambers
16
a
,
16
b
for carrying out the etching process to form the metal pattern, ashing chambers
18
a
,
18
b
for stripping the remaining photoresist pattern after the etching process and for passivation, and a cooling chamber
22
. Utility lines are connected to each chamber, if necessary.
FIG. 2
shows the structure of the etching chamber
16
a
shown in
FIG. 1
, which is a MERIE (Magnetron Enhanced Reactive Ion Etch) type dry etching chamber. The etching chamber employs radio frequency (RF) power to generate plasma for reactive ion etch under low pressure. Additionally, a magnetic coil
38
is further provided along the sidewall of the interior
30
of the etching chamber
16
a
as shown in FIG.
2
. The magnetic coil
38
generates a magnetic field in addition to the electric field generated in the chamber
16
a
by the RF power. The additional magnetic field focuses the ions around the sidewall of the interior
30
of the chamber
16
a
and forces the ions into the plasma formed at the center of the interior
30
of the chamber
16
a
. This increases the density of the plasma and keeps the plasma maintained for a longer period. Therefore, a high etch rate is achieved.
Referring to
FIG. 2
in more detail, a wafer
42
is mounted on an electrostatic chuck
46
. The electrostatic chuck
46
is installed over a cathode
48
at the center of the interior
30
of the chamber
16
a
, and a focus ring
44
is provided under the wafer
42
to facilitate the focusing of the plasma. High frequency power is applied on the cathode
48
and the focus ring
44
.
A chamber liner
32
is formed at the upper side of the chamber
16
a
. A gas disperse plate
34
for supplying processing gas over the wafer
42
is provided at the center of the chamber liner
32
, and the gas disperse plate
34
is connected to a gas supply line
36
.
On the sidewall of the interior
30
of the chamber
16
a
, a detector
40
for measuring the etch-end point is provided. On the bottom of the interior
30
of the chamber
16
a
, an exhaust port is provided and is connected to a turbo molecular pump
50
for maintaining a desired level of vacuum in the chamber
16
a.
The wafer
42
has a metal material layer formed on an insulating layer over the wafer, and a photoresist pattern is formed on the metal material layer to form a desired metal pattern. An etching process is carried out on the wafer
42
in the etching chamber
16
a
shown in
FIG. 2
while supplying processing gas. Chlorine (Cl
2
) gas and boron chloride (BCl
3
) gas is used as the processing gas for etching aluminum, which is generally used for metal patterns.
However, if gas including chlorine is used as the processing gas in the aluminum pattern formation process, corrosion problems occur in the metal pattern line because aluminum is subject to corrosion by the processing gas.
FIG. 3
is a plane-view of a wafer segment showing corrosion formed on a conventional aluminum pattern line. A metal pattern line
62
is formed on an insulating layer
60
over a semiconductor substrate. Parts of the aluminum pattern line
62
are corroded, which are shown as corrosion portions
69
in FIG.
3
. The corrosion portions
69
may expand, resulting in open circuits in the metal pattern line
62
. This causes electrical connection failure in semiconductor devices and reduces the production yield.
The corrosion failure in aluminum patterns is known to be caused by HCl which is created by the reaction of vapor with chlorine components in the photoresist and in the sidewall coating of the chamber or with AlCl
3
, a by-product of the etching process. Although a lot of study has been done on corruption failure, there is still no reliable explanation for the cause and no improvement.
Especially, U.S. Pat. No. 5,545,289 discloses a method of carrying out the ashing step by repeating passivation and stripping in order to reduce the corrosion failure. The ashing step is carried out to remove remaining photoresist patterns after the etching process on the metal material layer. However, the method does not solve the corrosion failure problem because it does not eliminate the cause of the corrosion failure.
Therefore, there has been a need for improving the systems and processes in order to reduce corrosion failure in aluminum pattern lines, thereby improving the reliability and the production yield of semiconductor devices.
SUMMARY OF THE INVENTION
It is a feature of the present invention to provide a metallization process that can reduce the corrosion failures in aluminum pattern lines, by suppressing any cause of the corrosion failures in an etching chamber in which the etching process for the metallization is carried out.
Another feature of the present invention is to provide a metallization process that can reduce the corrosion failures in aluminum pattern lines, by suppressing any cause of the corrosion failures in the transfer module and the load lock chamber, which are stand-by areas for the wafers before or after the etching process.
Still another feature of the present invention is to provide a system for forming metal patterns that can reduce the corrosion failures in aluminum pattern lines.
The metallization process for manufacturing semiconductor devices of the present invention comprises the steps of loading a semiconductor wafer into an etching chamber, the semiconductor wafer having a photoresist pattern formed over a metal material layer to be etched, stabilizing the environment in the etching chamber, main-etching the metal material layer to the etch-end point by using the photoresist pattern as an etch mask while supplying etching gas containing chlorine (Cl
2
) into the etching chamber, over-etching the metal material layer for a certain period of time over the etch-end point to form a metal pattern, purging the etching chamber after the over-etching step, and unloading the water from the etching chamber.
The metal material layer to be etched contains aluminum, and the etching gas contains boron chloride (BCl
3
) and chlorine (Cl
2
). The etching chamber is purged by supplying purified nitrogen (PN
2
) gas into the chamber.
In another aspect of the present invention, the metallization process for manufactu

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