Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2002-11-06
2004-12-07
Nhu, David (Department: 2818)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S697000
Reexamination Certificate
active
06828227
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the manufacturing of semiconductor devices. More particularly, the present invention relates to an improved method and mechanism using a resilient flexible material member under a wafer during wafer processing for the planarization of surfaces in the manufacturing of a semiconductor.
2. State of the Art
Typically, integrated circuits are manufactured by the deposition of layers of predetermined materials to form the desired circuit components on a silicon wafer semiconductor substrate. As the layers are deposited on the substrate wafer to form the desired circuit component, the planarity of each of the layers is an important consideration because the deposition of each layer produces a rough, or nonplanar, topography initially on the surface of the wafer substrate and, subsequently, on any previously deposited layer of material. Typically, photolithographic processes are used to form the desired circuit components on the wafer substrate. When such photolithographic processes are pushed to their technological limits of circuit formation, the surface on which the processes are used must be as planar as possible to ensure success in circuit formation. This results from the requirement that the electromagnetic radiation used to create a mask, which is used in the formation of the circuits of the semiconductor devices in wafer form, must be accurately focused at a single level, resulting in the precise imaging over the entire surface of the wafer. If the wafer surface is not sufficiently planar, the resulting mask will be poorly defined causing, in turn, a poorly defined circuit which may malfunction. Since several different masks are used to form the different layers of circuits of the semiconductor devices on the substrate wafer, any nonplanar areas of the wafer will be subsequently magnified in later deposited layers.
After layer formation on the wafer substrate, either a chemical etch-back process of planarization, a global press planarization process typically followed by a chemical etch-back process of planarization, or a chemical mechanical planarization process, may be used to planarize the layers before the subsequent deposition of a layer of material thereover. In this manner, the surface irregularities of a layer may be minimized so that subsequent layers deposed thereon do not substantially reflect the irregularities of the underlying layer.
One type of chemical etch-back process of planarization, illustrated in EUROPEAN PATENT APPLICATION 0 683 511 A2, uses a coating technique in which an object having a flat surface is used to planarize a coating material applied to the wafer surface prior to a plasma reactive ion etching process being used to planarize the wafer surface. Often, however, the planarization surface will contain defects, such as pits or other surface irregularities. These may result from defects in the flat surface used for planarizing or from foreign material adhering to the flat surface. The etching of such a wafer surface having irregularities will, at best, translate those undesirable irregularities to the etched surface. Further, since some etching processes may not be fully anisotropic, etching such irregular surfaces may increase the size of the defects in the etched wafer surface.
One type of global press planarization process, illustrated in U.S. Pat. No. 5,434,107, subjects a wafer, with features formed thereon having been coated with an inter-level dielectric material, to an elevated temperature while an elevated pressure is applied to the wafer using a press until the temperature and pressure conditions exceed the yield stress of the upper film on the wafer so that the film will attempt to be displaced into and fill both the microscopic and local depressions in the wafer surface. It should be noted that the film is only deformed locally on the wafer, not globally, during the application of elevated temperature and pressure since the object contacting the surface of the wafer only contacts the highest points or areas on the surface of the wafer deforming and displacing such points or areas of material locally, not globally displacing the material on the entire wafer surface. Other nonlocal depressions existing in the wafer are not affected by the pressing as sufficient material is not displaced thereinto. Subsequently, the temperature and pressure are reduced so that the film will become firm again thereby leaving localized areas having a partially planar upper surface on portions of the wafer while other portions of the wafer surface will remain nonplanar.
In one instance, global planar surfaces are created on a semiconductor wafer using a press located in a chamber. Referring to drawing
FIG. 1
, a global planarization apparatus
100
is illustrated. The global planarization apparatus
100
serves to press the surface of a semiconductor wafer
120
having multiple layers including a deformable outermost layer
122
against a fixed pressing surface
132
. The surface of the deformable layer
122
will assume the shape and surface characteristics of the pressing surface
132
under the application of force to the wafer
120
. The global planarization apparatus
100
includes a fully enclosed apparatus having a hollow cylindrical chamber body
112
and having open top and bottom ends,
113
and
114
, respectively, interior surface
116
and an evacuation port
111
. A base plate
118
having an inner surface
117
is attached to the bottom end
114
of chamber body
112
by bolts
194
. A press plate
130
is removably mounted to the top end
113
of chamber body
112
with pressing surface
132
facing base plate
118
. The interior surface
116
of chamber body
112
, the pressing surface
132
of press plate
130
and the inner surface
117
of base plate
118
define a sealable chamber. Evacuation port
111
can be positioned through any surface, such as through base plate
118
, and not solely through chamber body
112
.
The press plate
130
has a pressing surface
132
with dimensions greater than that of wafer
120
and being thick enough to withstand applied pressure. Press plate
130
is formed from nonadhering material capable of being highly polished so that pressing surface
132
will impart the desired smooth and flat surface quality to the surface of the deformable layer
122
on wafer
120
. Preferably, the press plate is a disc-shaped quartz optical flat.
A rigid plate
150
having top and bottom surfaces
152
and
154
, respectively, and lift pin penetrations
156
therethrough is disposed within chamber body
112
with the top surface
152
substantially parallel to and facing the pressing surface
132
. The rigid plate
150
is constructed of rigid material to transfer a load under an applied force with minimal deformation.
A uniform force is applied to the bottom surface
154
of rigid plate
150
through the use of an arrangement of bellows
140
and relatively pressurized gas to drive rigid plate
150
toward pressing surface
132
. Relative pressure can be achieved by supplying gas under pressure or, if the chamber body
112
is under vacuum, allowing atmospheric pressure into bellows
140
to drive the same. The bellows
140
is attached at one end to the bottom surface
154
of rigid plate
150
and to the inner surface
117
of base plate
118
with a bolted mounting plate
115
to form a pressure containment that is relatively pressurized through port
119
in base plate
118
. One or more brackets
142
are mounted to the inner surface
117
of the base plate
118
to limit the motion toward base plate
118
of the rigid plate
150
, when bellows
140
is not relatively pressurized. The application of force through the use of a relatively pressurized gas ensures the uniform application of force to the bottom surface
154
of rigid plate
150
. The use of rigid plate
150
will serve to propagate the uniform pressure field with minimal distortion. Alternately, the bellows
140
can be replaced by any suitable means for deliverin
Blalock Guy T.
Carroll Lynn J.
Stroupe Hugh E.
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