Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – Having glow discharge electrode gas energizing means
Reexamination Certificate
2001-09-14
2003-04-29
Dang, Thi (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
Having glow discharge electrode gas energizing means
C156S345470
Reexamination Certificate
active
06554952
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to semiconductor processing and, more particularly to methods for etching gold layers in an IC layer stack.
In semiconductor IC fabrication, devices such as component transistors are formed on a semiconductor wafer or substrate, which is typically made of silicon. Metallic interconnect lines, which are etched from a metallization layer disposed above the substrate, are then employed to couple the devices together to form a desired circuit. Most commonly, metallization layers are made from aluminum or aluminum alloys, but there is increasing use of other metals such as copper and gold. To facilitate discussion,
FIG. 1A
illustrates a cross-sectional view of a prior art integrated circuit structure
100
, representing the layers formed during the fabrication of a typical semiconductor IC having a gold layer.
A substrate
102
forms a base for an integrated circuit structure
100
. A gold layer
104
is shown formed over the surface of the substrate
102
. A hardmask layer
106
(typically an oxide layer) is disposed above the gold layer
104
, and an overlying photoresist layer
108
is formed over the hardmask layer
106
.
The photoresist layer
108
represents a layer of conventional resist material that may be patterned using patterned reticles and a stepper that passes light (e.g., ultra-violet light) onto the surface of the photoresist layer
108
. The layers of the integrated circuit structure
100
are readily recognizable to those skilled in the art and may be formed using any number of known deposition processes, including chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), and physical vapor deposition (PVD) such as sputtering.
To etch the hardmask layer, the photoresist layer
108
is patterned with a suitable photolithography technique, and subsequently the exposed hardmask layer is etched.
FIG. 1B
shows a cross-sectional view of the prior art integrated circuit structure
100
after etching the oxide hardmask layer
106
to form a hardmask for the underlying gold layer
104
.
Conventionally, gold layers have been etched using a Cl
2
chemistry at elevated temperatures of about 200° C. At such high temperatures, an oxide hardmask must be employed because of the relatively high etch rate ratio of gold to oxide and the low selectivity to organic photoresist.
FIG. 1C
shows a cross-sectional view of the prior art integrated circuit structure
100
after etching the gold layer using a Cl
2
chemistry at an elevated temperature of about 200° C. The elevated temperature Cl
2
etch provides a reasonable etch rate, however, profile control is severely limited and special high temperature reactor configurations must be used.
Due to equipment design and process throughput, a lower temperature etch process is often used to etch metallization layers. However, at lower temperatures a gold etch process using an oxide hardmask is not efficient. Thus, titanium hardmask layers are typically employed to etch metallization layers at lower temperatures of about 70° C.
FIG. 2A
shows a cross-sectional view of a prior art integrated circuit structure
200
, representing the layers formed during the low temperature fabrication of a typical semiconductor IC having a gold layer, after etching a titanium hardmask layer
202
.
The integrated circuit structure
200
includes a substrate
202
, a gold layer
204
formed over the surface of the substrate
202
, a titanium hardmask layer
206
disposed above the gold layer
204
, and an overlying photoresist mask
208
formed over the titanium hardmask layer
206
. As discussed above, the titanium hardmask layer
206
is patterned utilizing the photoresist mask
208
. However, at low temperatures the Chlorine in a conventional Cl
2
chemistry attacks the titanium hardmask at the same time it etches the gold layer, resulting in poor selectivity between the gold layer
204
and the titanium hardmask layer
206
. Thus, the titanium hardmask is etched away before the gold layer plasma etch process is finished, resulting in a damaged gold layer
204
after plasma etch, as shown in FIG.
2
B.
In view of the forgoing, what is needed are improved methods and apparatuses for etching a gold layer utilizing a titanium hardmask. Further, there is a need for methods and apparatuses that allow etching of a gold layer at conventional or near conventional lower electrode temperatures.
SUMMARY OF THE INVENTION
The present invention fills these needs by providing a gold etching chemistry that can be used at conventional or near conventional electrode temperatures and provides greatly improved mask selectivity with respect to a titanium hardmask. In one embodiment, a method for anisotropically etching a gold layer through an aperture in a hardmask is provided. A substrate is introduced into a processing chamber in preparation for a gold etch. The substrate includes a gold layer, a hardmask layer containing titanium formed above the gold layer, and an overlying photoresist mask disposed above the hardmask layer. The hardmask layer is then etched through the photoresist mask to create a hardmask for the underlying gold layer. Finally, a plasma is created within the processing chamber from an oxidizing gas and an etching gas. The etching gas is preferably a hydrochloric acid containing gas which may contain a chlorine containing gas. In addition, N
2
may also be provided. The plasma is then used to etch the gold layer through the hardmask.
In another embodiment, a system for etching gold layers is provided. The gold layer etch system includes a chamber receptive to a substrate having a gold layer and an overlying hardmask containing titanium. Also included in the gold etch system is a gas inlet mechanism connecting an oxidizing gas and an etching gas source to the chamber. The etching gas is preferably a hydrochloric acid containing gas which may contain a chlorine containing gas. In addition, N
2
may also be provided. Further included in the system is a pair of electrodes disposed within the chamber, and an RF generator coupled to the electrode pair so that a plasma is formed with the oxidizing gas and the etching gas which etches exposed portions of the gold layer through the hardmask.
In yet a further embodiment of the present invention an integrated circuit having a gold layer formed in a plasma processing chamber is disclosed. In this embodiment, the substrate, from which the integrated circuit is later formed, is introduced into a processing chamber. The substrate includes an underlying gold layer, a hardmask layer containing titanium, and an overlying photoresist mask formed above the hard mask layer. The hardmask layer is then etched through the photoresist mask to create a hardmask. Next, a plasma is created within the processing chamber from an oxidizing gas and an etching gas. The etching gas is preferably a hydrochloric acid containing gas which may contain a chlorine containing gas. N
2
may also be provided. The plasma is then used to etch the gold layer through the hardmask. Finally, the substrate is further processed to form an integrated circuit.
Advantageously, the improved titanium hardmask selectivity of the present invention allows the etching of a gold layer at conventional or near conventional lower temperatures, thus avoiding the need for special high temperature reactor configurations. This and other advantages of the present invention will become apparent to those skilled in the art upon a reading of the following description and a study of the various figures of the drawings.
REFERENCES:
patent: 5900103 (1999-05-01), Tomoyasu et al.
Goldspring Greg
Lo Gladys So-Wan
Mytton David W.
Dang Thi
Lam Research Corporation
Martine & Penilla LLP
LandOfFree
Method and apparatus for etching a gold metal layer using a... 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 and apparatus for etching a gold metal layer using a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for etching a gold metal layer using a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3050860