Semiconductor device

Details Semiconductor device Semiconductor device

2001-05-04

2002-07-23

Meier, Stephen D. (Department: 2822)

Active solid-state devices (e.g., transistors, solid-state diode

Combined with electrical contact or lead

Of specified material other than unalloyed aluminum

C257S754000

Reexamination Certificate

active

06424041

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a semiconductor device. More particularly, the present invention relates to a semiconductor device that prevents copper of copper wiring from diffusing into a memory storage portion for storing information.
2. Description of the Background Art
With ever-increasing demand to shrink the semiconductor devices in dimensions, the wiring width: has been reduced. Moreover, a wiring material has increasingly changed from aluminum wiring to copper wiring in order to reduce the electrical resistance and also the wiring width. The copper wiring has a reduced wiring width mainly because of the damascene method. Replacing aluminum wiring with copper wiring has the following benefits:
(a) Electrical resistance of the wiring can be reduced, so that the wiring delay time is reduced, and an operation frequency can be increased, resulting in an increased operating speed of the semiconductor device. Reduction in electrical resistance also results in reduced capacity between adjacent wires, whereby the wiring delay time can further be reduced;
(b) Reduction in electrical resistance results in reduced power consumption, and also enables the amount of heat generation to be reduced even with a higher integration degree; and
(c) The copper wiring is, normally formed according to the damascene method, so that the copper wiring width can be reduced, resulting in a dimensionally shrunk semiconductor device.
However, copper atoms have a property of easily diffusing into silicon and a silicon oxide film. Therefore, a copper bridge is formed between copper wires, causing short-circuit thereof. Moreover, the copper atoms get into an active region of the silicon substrate, resulting in unsatisfactory characteristics and malfunctioning.
Accordingly, some proposals have been made in order to prevent characteristics of the semiconductor device from being degraded by diffusion of copper atoms from copper wiring through silicon into an active region or the like. For example, the following proposal has been made in order to prevent copper diffusion from a copper-film wiring pattern into an active region of the semiconductor substrate: more specifically, a proposal has been made to form an amorphous barrier film on top and bottom of a copper wiring pattern formed in an upper layer (Japanese Patent Laying-Open No. 10-256256). According to this method, copper does not diffuse from the top and bottom surfaces of the copper film. In addition, the following proposal has been made in order to prevent copper diffusion from a copper wiring layer into a silicon substrate: first, a copper-diffusion barrier film is formed, on the sidewall of a contact hole formed in an interlayer insulating layer and on the bottom and sidewall of a patterned wiring groove in the interlayer insulating layer. Then, a metallic compound mainly comprised of copper is embedded thereon, so that an embedded wiring layer is formed (Japanese Patent Laying-Open No. 10-98011). According to this method, copper does not diffuse downward from the embedded copper wiring layer, and therefore characteristics of an underlying active layer are not degraded. Moreover, the following proposal has been made in order to prevent copper atoms from diffusing from copper wiring into a silicon substrate and oxide film: a copper-diffusion barrier film is formed on the bottom and sidewall of a wiring groove formed in an interlayer insulating film. Then, a,copper film is formed thereon and heated for reflow, so that the copper film is embedded in the wiring groove (Japanese Patent Laying-Open No. 8-148560). This method also prevents the copper atoms from diffusing from the copper film, the wiring layer, into an underlying active region.
However, with the progress in dimensional shrinking of the semiconductor devices, a problematic amount of copper has become far smaller than that is conventionally problematic. More specifically, as shown in
FIG. 22
, in the case where the copper wiring is used in, e.g., a DRAM (Dynamic Random Access Memory), copper atoms get into capacitors of a memory cell portion in the DRAM, destroying charges corresponding to information. A capacitor has a dielectric film interposed between electrodes, and stores 1-bit information according to presence/absence of accumulated charges in the electrodes. The copper atoms getting into the capacitor cause dissipation of charges within the dielectric, destroying an information storage function. In
FIG. 22
, a wiring portion
150
is provided over a memory cell portion
130
and a peripheral circuit portion
140
, and copper wires
116
a
and
116
b
for connecting the corresponding contacts are provided in the wiring portion
150
. The copper wires
116
a
and
116
b
in the peripheral circuit portion are connected through corresponding contacts
109
c
and
113
c
to corresponding source/drain regions
106
formed with a respective gate electrode
104
interposed therebetween. Gate electrodes
104
are arranged in the memory cell portion
130
, and a lift pad
108
extends from each active region located between the gate electrodes
104
. A capacitor contact
111
is formed on the lift pad
108
, and a capacitor
112
comprised of a lower electrode
112
a
, a dielectric
112
b
and an upper electrode
112
c
is connected thereto. When this semiconductor device is subjected to heat during the manufacturing process, copper atoms diffuse from the copper film into the capacitors in the memory cell portion
130
. Moreover, while the finished semiconductor device is in use, the copper atoms move into the capacitors due to electrodiffusion. The capacitors are destroyed even when the above-mentioned conventional measures are taken to prevent copper diffusion. Accordingly, the problematic amount of copper herein is far smaller than the conventionally problematic amount. Therefore, in the field of semiconductor devices, development of semiconductor devices sustaining a stable memory cell operation for a long time while still having the above-mentioned benefits of copper wiring has been strongly demanded.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a semiconductor device capable of reliably preventing diffusion of copper atoms even in a slight amount, and also capable of easily forming means for preventing the copper diffusion.
The semiconductor device of the present invention has a memory storage portion and a wiring portion including a copper wire apart from the memory storage portion on a semiconductor substrate. The semiconductor device includes copper diffusion blocking means provided in a region surrounding the memory storage portion for blocking copper diffusion from the wiring portion toward the memory storage portion.
The region surrounding the memory storage region is located away from the copper wire. Therefore, in this region, the driving force for diffusion of copper atoms is small. Since the copper-diffusion blocking means is provided in this region, diffusion of copper atoms can be reliably prevented even in a slight amount. Moreover, the copper-diffusion blocking means provided in this region allows for a simple structure that is easy to produce. Therefore, with the copper-diffusion blocking means having a simple shape, diffusion of copper atoms into the memory storage portion that destroys information therein can be prevented while still enjoying the benefits of copper wiring.
The memory storage portion as used herein mainly indicates a memory storage portion of the type that stores information corresponding to presence/absence of charges. However, the present invention is not limited to this. Semiconductor devices for storing information corresponding to presence/absence of charges include a DRAM (Dynamic Random Access Memory), EPROM (Erasable Programmable Read Only Memory) including a flash memory, EEPROM (Electrically Erasable Programmable Read Only Memory), and charge-transfer sequential access memory. When copper gets into the memory storage portion of this type, the

Affiliated with

Also associated with

Rating

Semiconductor device does not yet have a rating. At this time, there are no reviews or comments for this patent.

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

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2887907