Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Of specified configuration
Reexamination Certificate
1998-07-10
2001-11-13
Loke, Steven (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Of specified configuration
C257S773000, C257S786000
Reexamination Certificate
active
06316835
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to a method for forming an opening in a semiconductor structure and more particularly, relates to a method for forming a zig-zag bordered opening in a semiconductor structure for a bond pad such that when a tungsten plug is subsequently formed therein, the stress in an underlying layer of titanium nitride is reduced to avoid the formation of volcano defect.
BACKGROUND OF THE INVENTION
In the fabrication of semiconductor devices, connections to the semiconductor device are typically accomplished by metallic connection points or bond pads (I/O pads) that are disposed on a planar surface of the device (or die) around the periphery thereof. Once the functionality and the circuit requirements of a semiconductor device are met in the design, the required number of bond pads for operating the device can be determined. The bond pads are normally positioned on a semiconductor device in a peripheral area which is a ring-shaped area on the surface of the device or a narrow band between the edges of the device and an interior area of the device. One of the reasons that bond pads are disposed around the edges of a device is that the peripheral location permits a relatively large number of I/O connections to the die without causing the connections to cross one another.
Bond pads are formed in a metal conductor layer deposited and then patterned on the top surface of a semiconductor device. The metal conductor layer is frequently embedded in an insulating layer of a dielectric material. In order to establish electrical communication with the bond pads, a contact plug is normally used which is formed of a conductive metal material such as tungsten or aluminum.
The bond pad openings (or contact openings), when filled with an appropriate conductive material form void-free contact plugs and exhibit low contact resistance to the underlying and overlying conductors. Other than metallic materials such as tungsten and aluminum, heavily doped polysilicon can also be used in contact plugs. For instance, polysilicon can be doped n-type when contacting N-regions and p-type for P-regions to avoid inter-diffuision and dopant migration. When a metallic material such as tungsten or aluminum is used to fill a contact window, the window is typically lined with a thin layer of titanium or titanium/titanium nitride (TiN) prior to the contact plug fill. Other similar compositions such as titanium tungsten and tungsten can also be used. The main purpose of titanium is to improve the contact resistance. The TiN film is deposited to act as a diffusion barrier to certain elements such as silicon from the substrate and fluorine generated during a tungsten chemical vapor deposition process. The thin layer of Ti or TiN also act as a glue layer to improve adhesion to tungsten. The layers may further act as a wetting film to enhance the reflow of aluminum. The liner of Ti and TiN are typically deposited by a collimated sputtering process or a chemical vapor deposition process. A desirable thickness for the Ti layer is between about 200 Å and about 800 Å, while the same for the TiN layer is between about 800 Å and about 2500 Å.
Contact hole openings can be filled by depositing tungsten in a chemical vapor deposition or a sputtering process and then planarizing the metal by etching it back to the insulator surface or by a chemical mechanical polishing process such that only tungsten is left in the contact openings. Tungsten CVD is used for contact hole filling and is typically performed by the pyrolitic decomposition of tungsten hexafluoride (WF
6
), or by the reduction of WF
6
with hydrogen, silicon or silane. In semiconductor manufacturing, reduction WF
6
at a temperature between 250° C.~600° C. is more frequently used.
In the tungsten plug process, TiN is used as a barrier layer and a glue layer. However, TiN grains have a columnar structure which allows fluorine from the reaction precursor to easily migrate through the crevices of TiN to react with an underlying titanium layer during the tungsten deposition process. The fluorine causes the peeling of the glue layer TiN and the tungsten layer deposited. A conventional tungsten plug formation that has the volcano defect is shown in FIG.
1
.
FIG. 1
illustrates a semiconductor device that is built on a semi-conducting substrate
12
. A contact hole
14
is opened through an inter-level dielectric layer
16
to provide communication with the source/drain active region
20
. Inside the contact hole and on top of the inter-level dielectric layer
16
, barrier layers of titanium
22
and titanium nitride
24
are deposited. A layer of conductive metal such as tungsten
32
is then deposited bya chemical vapor deposition (CVD) process over the surface of the substrate
12
to fill the contact hole
14
.
During the tungsten CVD process, fluorine from the reactant precursor WF
6
migrate through the TiN film
24
to react with the titanium layer
22
and cause the peeling of the tungsten and the TiN layer from the substrate
12
. This is shown in FIG.
1
. The volcano effect, shown as
30
in
FIG. 1
, reflects the delamination of the tungsten and titanium nitride layers from the substrate
12
. The two layers are separated or peeled away from the substrate
12
. It is believed that during tungsten CVD WF
6
reacts with the underlying layer of Ti to produce W and TiF
3
. Since TiF
3
is a material that has poor adhesion to tungsten, it does not adhere to and peels away from the tungsten layer
22
. A plane view of a semiconductor structure having typical bond pad openings is illustrated in
FIG. 2
, showing the openings are formed by straight line borders. The black dots shown in
FIG. 2
along the bond pad openings are the volcano defects.
Others have attempted to improve the tungsten plug process and to avoid the volcano defect. One such method is an annealing process of a rapid thermal annealing method to improve the density and thus to reduce voids in a TiN film. The theory is that oxygen or nitrogen products can be used to stuff the TiN grain boundaries such that fluorine cannot penetrate through. However, the annealing method is a time-consuming process which creates a bottle neck in the total semiconductor fabrication process.
It is therefore an object of the present invention to provide a method for forming bond pad windows in a semiconductor structure that does not have the drawbacks and shortcomings of the conventional tungsten plug process.
It is another object of the present invention to provide a method for forming bond pad windows in a semiconductor structure that provides windows of reduced stress in the underlying TiN barrier layer without the formation of volcano defect.
It is a further object of the present invention to provide a method for forming bond pad windows in a semiconductor structure that does not create straight-line border bond pad openings.
It is another further object of the present invention to provide a method for forming zig-zag bordered opening in a semiconductor structure that creates openings of substantially reduced stress in an underlying TiN barrier layer.
It is still another object of the present invention to provide a method for forming zig-zag bordered openings in a semiconductor structure that creates openings having saw-tooth configuration in the borders of the openings.
It is yet another object of the present invention to provide a method for forming zig-zag bordered bond pad openings in a semiconductor structure wherein the pitch of the zig-zag border created between about 2 micron and about 6 micron.
SUMMARY OF THE INVENTION
In accordance with the present invention, a method for forming a zig-zag bordered opening in a semiconductor structure to reduce the stress in a titanium nitride film in the opening such that the peeling of the titanium nitride film and a subsequently deposited tungsten metal plug can be prevented to avoid the volcano defect.
In a preferred embodiment, a method for forming a zig-zag bordered opening in a semiconductor st
Chang W. R.
Chao Y. C.
Chen C. H.
Tsui Y. M.
Loke Steven
Taiwan Semiconductor Manufacturing Company Ltd
Tung & Associates
LandOfFree
Method for forming zig-zag bordered openings in... 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 for forming zig-zag bordered openings in..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for forming zig-zag bordered openings in... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2594402