Coating apparatus – Gas or vapor deposition – Having means to expose a portion of a substrate to coating...
Reexamination Certificate
1999-08-27
2001-03-27
Lund, Jeffrie R. (Department: 1763)
Coating apparatus
Gas or vapor deposition
Having means to expose a portion of a substrate to coating...
C118S728000, C118S729000, C118S730000, C118S715000, C118S500000, C118S504000, C204S298070, C204S298110, C204S298150
Reexamination Certificate
active
06206976
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to semiconductor processing and manufacture, and, more particularly, to an apparatus and method for excluding undesired deposition near a wafer edge.
BACKGROUND OF THE INVENTION
Integrated circuits are used in many electronic devices. A typical integrated circuit includes a semiconductor substrate including active regions, and one or more interconnect layers formed on the substrate. The adjacent interconnect layers are typically separated by an interlevel dielectric layer. A semiconductor wafer including a plurality of integrated circuit die may be positioned into a plasma deposition chamber to deposit some of the desired layers. The wafer is cut after processing into the discrete integrated circuit die.
Tungsten, tungsten silicide and titanium nitride, for example, are metals that are conventionally deposited on the wafer by chemical vapor deposition (CVD) during manufacturing. These metals may be deposited in a reaction chamber that holds from one to several wafers, and which also supplies an elevated temperature and/or plasma to enhance the deposition. Unfortunately, such metals would also be deposited on the edge and backside of the wafer if these areas were unprotected during CVD. The metals tend to peel and flake and would contaminate other portions of the wafer during subsequent processing steps. Also, any residual metal can be sputtered back onto the surface during subsequent processing steps.
One approach to preventing undesired deposition on the backside and particularly the edge of the wafer is disclosed, for example, in U.S. Pat. No. 5,843,233 to van de Ven et al. and assigned to Novellus Systems, Inc. Novellus also offers the system described in the patent as its minimal overlap exclusion ring (MOER) process. The apparatus includes a chamber for positioning of five wafers therein, a pedestal to support each wafer, and an exclusion ring for each wafer.
The exclusion ring includes an extension which slightly overlaps the front peripheral region of the wafer and defines a restrictive gap or opening therewith. So-called deposition control gas is introduced under the exclusion guard extension and exits through the gap. Orifices may be provided through the extension to further increase uniformity of deposition on the front of the wafer adjacent the edge.
To increase the useable area on the wafer, the deposition is desirably uniform until reaching the edge. For example, for a 200 mm wafer, a 6 mm ring of the wafer was left unusable in the past. More recently, the ring is now desirably reduced to only 4 mm. Many wafers include beveled edges which complicates the mechanics of deposition edge exclusion. In addition, a typical deposition chamber is desirably used for a number of different processes, some with slower deposition rates, and others with faster rates. Unfortunately, to accommodate different processes typically requires compromising flow rates and deposition chemistry to ensure proper edge exclusion. In addition, as the chamber is continually used, deposits also tend to build-up on the surfaces of the exclusion ring. Accordingly, these must be periodically cleaned to ensure adequate performance. Opening the chamber for such cleaning may result in many hours of downtime for the apparatus. Changing the rings to substitute others with different dimensions would also entail significant apparatus downtime, and is therefore impractical.
SUMMARY OF THE INVENTION
In view of the foregoing background, it is therefore an object of the invention to provide an apparatus and method for providing edge deposition exclusion in wafer processing, and while permitting control of the edge exclusion effect.
This and other objects, features and advantages in accordance with the present invention are provided by a controllable edge exclusion assembly for controllably excluding deposition adjacent a peripheral edge of a wafer within a deposition chamber and based upon fluid flow. More particularly, the controllable edge exclusion assembly preferably comprises a ring-shaped body extending inwardly from the peripheral edge of the wafer and spaced above an adjacent front surface of the wafer. The ring-shaped body may have a plurality of fluid passageways extending therethrough so that fluid flow from adjacent a back surface of the wafer passes over the peripheral edge of the wafer and through the fluid passageways to thereby exclude deposition adjacent the peripheral edge of the wafer. Moreover, the assembly also preferably further includes a flow controller associated with the fluid passageways of the ring-shaped body for controlling fluid flow therethrough. Accordingly, the edge exclusion effect can be controlled without changing out fixed-dimension exclusion rings. The temperature, deposition flow rates, and chemistry can be adjusted to optimize film properties, while the edge exclusion can be controlled relatively independently in accordance with the invention.
In one embodiment, the flow controller comprises a control body having a plurality of fluid passageways therein, and the control body is relatively movable with respect to the ring-shaped body. This relative movement provides a selectable amount of alignment between the fluid passageways of the control body and the ring-shaped body to thereby control fluid flow. In one particularly advantageous variation, the control body and the ring-shaped body are relatively rotatable. For example, the ring-shaped body may be fixed relative to a wafer support, and the control body may be rotatable relative to the ring-shaped body.
The control body may be positioned adjacent an upper surface of the ring-shaped body opposite the wafer. In addition, the fluid passageways of the control body may have a substantially same cross-sectional area as the fluid passageways of the ring-shaped body. In another variation, at least one of the control body and the ring-shaped body has a plurality of sets of fluid passageways therein of different cross-sectional areas. These different sets can be selectively connected in alignment with opposing passageways to thereby control flow. The control body may also have a ring shape.
The flow controller also preferably comprises a drive device for relatively moving the control body and ring-shaped body responsive to control signals. These control signals may be generated externally from the deposition chamber. Accordingly, the flow rate can be set without opening the deposition chamber and suffering the resultant apparatus downtime.
In another embodiment of the invention, the flow controller comprises respective iris diaphragms for the fluid passageways. The cross-sectional open area of the iris diaphragms may be controlled to control fluid flow. Of course, in this embodiment, the flow controller also preferably includes a drive device for controlling the iris diaphragms responsive to control signals. These control signals can also be generated externally from the deposition chamber.
A method aspect of the invention is for deposition exclusion adjacent a peripheral edge of a wafer within a deposition chamber and based upon fluid flow. The method preferably comprises the steps of: positioning a ring-shaped body extending inwardly from the peripheral edge of the wafer and spaced above an adjacent front surface of the wafer, the ring-shaped body having a plurality of fluid passageways extending therethrough; setting a flow controller associated with the fluid passageways of the ring-shaped body for a desired fluid flow therethrough; and generating a fluid flow from adjacent a back surface of the wafer to pass over the peripheral edge of the wafer and through the fluid passageways of the ring-shaped body to thereby exclude deposition adjacent the peripheral edge of the wafer.
In one embodiment, the flow controller comprises a control body having a plurality of fluid passageways therein and being relatively movable with respect to the ring-shaped body. Accordingly, the step of setting the flow controller comprises relatively moving the control body to provide a selected a
Crevasse Annette Margaret
Gould-Choquette Adrienne
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Lucent Technologies - Inc.
Lund Jeffrie R.
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