Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2002-10-11
2004-09-14
Pert, Evan (Department: 2829)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
Reexamination Certificate
active
06790763
ABSTRACT:
TECHNICAL FIELD
This invention relates to a substrate processing method, and more particularly, to those used to fill fine recesses formed on the surface of a semiconductor substrate with copper, thereby forming a copper interconnection pattern.
BACKGROUND ART
In recent years, with the increased throughput and the higher integration of semiconductor chips, moves to use copper (Cu) with low electric resistivity and high electromigration resistance as a metallic material for forming an interconnection circuit on a semiconductor substrate, instead of aluminum or aluminum alloy, have become noticeable. A copper interconnection of this type is generally formed by filling fine recesses formed on the surface of the substrate with copper. Methods for forming the copper interconnection include CVD, sputtering, and plating.
FIGS. 62A
to
62
C show an example to form a copper interconnection by copper plating in the sequence of steps. As shown in
FIG. 62A
, an insulating film
2
of SiO
2
is deposited on a conductive layer
1
a
on a semiconductor substrate
1
having formed a semiconductor device. A contact hole
3
and a trench
4
for an interconnection are formed in the insulating film
2
by lithography and etching technology. A barrier layer
5
of TaN or the like is formed on the contact hole
3
and the trench
4
, and a copper seed layer
7
is further formed thereon as a power supply layer for electroplating.
As shown in
FIG. 62B
, copper plating is applied to the surface of a semiconductor substrate W to fill copper into the contact hole
3
and the trench
4
of the semiconductor substrate
1
and also deposit a copper film
6
on the insulating film
2
. Then, the copper film
6
and the barrier layer
5
on the insulating film
2
is removed by chemical mechanical polishing (CMP), thus making the surface of the copper film
6
filled into the contact hole
3
and the trench
4
for an interconnection lie flush with the surface of the insulating film
2
. In this manner, an interconnection composed of the plated copper film
6
is formed as shown in FIG.
62
C.
FIG. 63
shows the entire constitution of a substrate processing apparatus for performing the above series of interconnection formation steps in a clean room. In the clean room, an insulating film forming device
10
, a lithography and etching device
12
, a barrier layer forming device
14
, a copper seed layer forming device
26
, a copper plating device
18
, and a CMP device
20
are housed. The substrate W having the insulating film
2
formed by the insulating film forming device
10
is accommodated into a substrate cassette
22
, and transported to the lithography and etching device
12
for a subsequent step. The substrate W having the contact hole
3
and the trench
4
for an interconnection formed in the lithography and etching device
12
is transported, while being housed in the substrate cassette
22
, to the barrier layer forming device
14
for a subsequent step. The substrate W thus processed in the respective devices is transported, while being accommodated in the substrate cassette
22
, to subsequent steps, whereby the series of interconnection formation steps are sequentially performed.
FIG. 64
schematically shows a conventional general configuration of a copper plating device for use in the above type of copper plating. This plating device includes a cylindrical plating tank
602
opening upward and holding a plating liquid
600
inside, and a rotatable substrate holder
604
adapted to detachably hold a substrate W, such as a substrate, so as to face downward, and disposing the substrate W at a position at which it closes the upper end opening portion of the plating tank
602
. Inside the plating tank
602
, a flat plate-shaped anode plate (anode)
606
immersed in the plating liquid
600
to serve as an anodic electrode is horizontally placed, and the seed layer of the substrate W is to serve as cathodic electrode. The anode plate
606
comprises a copper plate or a gathering of copper balls.
A plating liquid supply pipe
610
having a pump
608
mounted inside is connected to the center of the bottom of the plating tank
602
. Outside of the plating tank
602
, a plating liquid receptacle
612
is placed. Further, the plating liquid which has flowed into the plating liquid receptacle
612
is returned to the pump
608
through a plating liquid return pipe
614
.
Because of this structure, the substrate W is held facedown at the top of the plating tank
602
by the substrate holder
604
, and rotated in this condition. With a predetermined voltage being applied between the anode plate
606
(anodic electrode) and the seed layer of the substrate W (cathodic electrode), the pump
608
is driven to introduce the plating liquid
600
into the plating tank
602
, whereby a plating electric current is flowed between the anode plate
606
and the seed layer of the substrate W to form a plated copper film on the lower surface of the substrate W. At this time, the plating liquid
600
which has overflowed the plating tank
602
is recovered by the plating liquid receptacle
612
, and circulated.
Copper easily diffuses into a silicon dioxide film during a semiconductor manufacturing process to deteriorate the insulating properties of the silicon dioxide film, and causes cross contamination during the steps of transportation, storage and processing of the substrate. Copper may also contaminate the interior of the clean room.
In detail, the substrate having the copper seed layer formed thereon used to be transported, while being placed in the substrate cassette, to the copper plating device, and the substrate having the copper film formed in the copper plating device used to be transported, while being put in the substrate cassette, to the CMP device. Thus, copper particles and copper ions adhering to the substrate, which are very active and harmful to other processes, were likely to diffuse into the clean room.
When a plated copper film is deposited on the surface of the substrate by use of a copper electroplating device, a voltage between the center of the seed layer of the substrate and the anode differs from a voltage between the periphery of the seed layer of the substrate and the anode, because of the electrical resistance of the copper seed layer formed on the surface of the substrate. Thus, the film thickness of the plated copper film on the periphery of the substrate is greater than the film thickness of the plated copper film at the center of the substrate.
When the plated copper film thicker on the periphery than at the center of the substrate is polished by a polishing device, the plated copper film remains unpolished on the periphery of the substrate, or the plated copper film at the center is scraped excessively, which is a phenomenon called dishing.
The distance between the anode and the substrate may be fully lengthened to increase the electric resistance of the plating liquid itself, thereby diminishing the influence of the electric resistance of the copper seed layer. This measure can make the film thickness of the plated copper film more uniform, but leads to upsizing of the apparatus.
DISCLOSURE OF INVENTION
The present invention has been accomplished in light of the foregoing circumstances. Its object is to provide a substrate processing method which can deposit the plated copper film on the surface of the substrate more uniformly; which can polish away a surplus plated copper film without leaving unscraped portions or causing dishing; and which can prevent the contamination of the interior of the clean room with hazardous copper coming from the copper film, such as the copper seed layer or copper film, formed on the surface of the substrate.
According to an aspect of the present invention, there is provided a method of filling a metal in fine trenches in a surface of a substrate, comprising: forming a barrier layer on the substrate, and a seed layer on the barrier layer; providing an electroplating apparatus having a first substrate holder for holding the substrate, a plating b
Inoue Hiroaki
Kondo Fumio
Mishima Koji
Suzuki Yoko
Tanaka Akira
Ebara Corporation
Harrison Monica D.
Pert Evan
Wenderoth , Lind & Ponack, L.L.P.
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