Method of forming metal lines

Details Method of forming metal lines Method of forming metal lines

1999-01-06

2001-03-06

Nelms, David (Department: 2818)

Semiconductor device manufacturing: process

Coating with electrically or thermally conductive material

To form ohmic contact to semiconductive material

C438S622000

Reexamination Certificate

active

06197676

ABSTRACT:

BACKGROUND OF THE INVENTION
1). Field of the Invention
This invention relates to a method of forming metal lines utilizing spacer technology.
2). Discussion of Related Art
Integrated circuits are manufactured by forming individual semiconductor electrical elements on a silicon substrate and interconnecting the electrical elements.
The electrical elements may comprise transistors, diodes, capacitors, etc. A dielectric material is deposited over the electrical elements. Conductive vias are formed which extend from contact surfaces of the electrical elements to an upper surface of the dielectric layer. The vias are then interconnected by a network of metal lines.
One method of forming metal lines involves a technique known as photolithography.
FIGS. 1A
to
1
C illustrate such a technique for forming metal lines.
FIG. 1A
shows a substrate
108
of the above kind on which a junction layer is deposited. A metal line has to be formed in the junction layer
110
. A photoresist layer
112
is deposited on the junction layer
110
and cured. A mask
114
is then positioned some distance above the photoresist layer
112
. The mask has opaque and transmissible regions. For purposes of illustration, the mask
114
in
FIG. 1A
has one or more openings
116
formed therein allowing the light through. A portion
118
of the photoresist layer is then chemically altered by radiating light at a selected frequency through the mask
114
.
FIG. 1B
shows the structure of
FIG. 1A
after an etching step. An etchant is used which removes the portion
118
which is chemically altered selectively over the rest of the photoresist layer
112
. The resulting photoresist layer
112
has a trench
120
where the portion
118
used to be. The photoresist is known as a positive resist when portions which are irradiated are removed. Negative resists may alternatively be used.
A hole
122
is then etched with the trench
120
providing alignment. The photoresist layer
112
is then stripped. A metal layer is then deposited over the junction layer
110
and in the hole
122
, and then polished back to leave a metal line in the hole
122
, as shown in FIG.
1
C. The metal line's dimensions depend on the way the photoresist layer
112
is photolithographically masked.
One problem with photolithography deals with control over the width of the openings
116
in the mask
114
when the mask
114
is made. A wider opening leads to a wider portion
118
being chemically altered, and to a wider eventual metal line in the hole
122
being formed.
Another problem with photolithography deals with the chemical composition of the photoresist layer
112
. Non-uniform curing of the photoresist layer
112
results in variations in the chemical composition in the area of the portion
118
being chemically altered. These variations in chemical composition result in variations in the width of the portion
118
, after being chemically altered, and in the width of the eventual metal line in the hole
122
.
A further problem with photolithography is that light passing through the mask
114
is subject to diffraction. Diffraction of the light results in the width of the portion
118
being different to the width of the opening
116
. The difference in the width of the portion
118
with respect to the width of the opening
116
is difficult to control or accurately determine. The mask
114
may also be spaced from the photoresist layer
112
in a non-uniform manner at different locations so that the width of the portion
118
varies along its length. Such variations in the width of the portion
118
along its length result in variations of the metal line in the hole
122
along its length in a manner generally referred to as “metal line thickness wobble”.
The above factors all result in metal lines with widths which are difficult to control. What is therefore required is a method of forming metal lines wherein the widths of the metal lines can be controlled more accurately, especially with respect to prior art techniques of forming metal lines involving photolithography.
SUMMARY OF THE INVENTION
The invention provides a method of forming a metal line. A step is formed on a substrate. According to one method of the invention a metal layer is formed on the substrate and on the step. The metal layer is then etched. A portion of the metal layer remains adjacent the step and the substrate is exposed adjacent the portion of the metal layer.


REFERENCES:
patent: 4843034 (1989-06-01), Herndon et al.
patent: 5384953 (1995-01-01), Economikos et al.
patent: 5422308 (1995-06-01), Nicholls et al.
patent: 5472901 (1995-12-01), Kapoor et al.
patent: 5846860 (1998-12-01), Shih et al.
patent: 5977638 (1999-11-01), Rodgers et al.

Affiliated with

Also associated with

Rating

Method of forming metal lines does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Method of forming metal lines, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of forming metal lines will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2456640