Substrate support member for a processing chamber

Details Substrate support member for a processing chamber Substrate support member for a processing chamber

2000-05-03

2002-10-15

Mills, Gregory (Department: 1763)

Coating apparatus

Gas or vapor deposition

Work support

C118S715000, C118S725000

Reexamination Certificate

active

06464795

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of semiconductor substrate processing equipment. More particularly, the present invention relates to an improved support member adapted for vacuum chucking of a substrate thereto and delivering a purge gas to the edge of a substrate supported thereon.
2. Background of the Related Art
In the fabrication of integrated circuits, equipment has been developed to automate substrate processing by performing a sequence of processing steps on a substrate without removing the substrate from a vacuum environment, thereby reducing transfer times and contamination of substrates. Such a vacuum system has been disclosed, for example, by Maydan et al. in U.S. Pat. No. 4,951,601, in which a plurality of processing chambers are connected to a central transfer chamber. A robot disposed in the central transfer chamber passes substrates through slit valve openings formed in the various connected processing chambers and retrieves the substrates after processing in the chambers is complete.
The processing steps carried out in the vacuum chambers typically require the deposition or etching of multiple metal, dielectric and semiconductive film layers on the surface of a substrate. Examples of such processes include chemical vapor deposition (CVD), physical vapor deposition (PVD), and etching processes. Although the present application primarily discusses CVD process chambers and systems, the present invention is equally applicable to other process chambers and systems.
CVD vacuum chambers are employed to deposit thin films on semiconductor substrates. Typically, a precursor gas is charged into a vacuum chamber through a gas manifold plate situated above the substrate, and the substrate is heated to process temperatures generally in the range of about 250° C. to about 650° C. The precursor gas reacts on the heated substrate surface to deposit a thin layer thereon.
In a typical process chamber, a support member, commonly formed of aluminum, ceramic, or other material, on which a substrate is mounted during processing is vertically movable in the chamber. A plurality of support fingers are also vertically movable by an elevator and extend through the support member to facilitate transfer of a substrate from a robot blade to the support member. Typically, the support member also acts as a heater plate that is heated by a resistive heating element located therein which provides sufficient heat to maintain the substrate at a desired process temperature. Further, a purge gas is delivered to a perimeter of the substrate to prevent deposition gases from contacting and depositing on the edge and backside of the substrate.
Substrate uniformity is dependent on uniform heating and uniform purge gas delivery, among other things. Various known methods and support member designs are employed in the prior art to ensure such uniformity. For example, to increase the heat transfer from the support member to the substrate, the substrate is typically adhered to the upper surface of the support member by a “vacuum chuck.” Typically, vacuum chucking is accomplished by applying a pressure differential between grooves formed in the upper surface of the support member and the process chamber. As shown in
FIG. 1
, the upper surface
12
of the support member
10
of a prior system includes a plurality of concentric grooves
14
formed therein which intersect a plurality of radial grooves
16
. A vacuum supply communicates with the grooves
14
,
16
through holes
18
disposed along the plurality of radial grooves
16
to supply a vacuum thereto. The plurality of radial grooves
16
extend to a diameter slightly less than the diameter of a substrate. Thus, the vacuum supply is able to create a low pressure environment under the substrate to chuck, or adhere, the substrate to the upper surface
12
. Pulling the substrate tightly against the upper surface
12
of the support member
10
enhances the surface to surface contact and, therefore, the heat transfer therebetween.
The purge gas channels
20
of the support member
10
are shown in
FIG. 1
by hidden lines
21
. The gas channels
20
comprise a complicated labyrinth of interconnected passageways constructed by drilling from the edge of the support member
10
inward. The gas channels
20
lead to a plurality of holes
22
disposed around the perimeter of the upper surface of the support member
10
which provide outlets for a purge gas delivered to the substrate edge. The gas is delivered from a gas source (not shown) to the gas channels
20
though a gas delivery channel formed in a shaft (also not shown) of the support member
10
.
One problem associated with current systems occurs as a result of cleaning the process chamber. During the deposition process, material such as tungsten, is deposited not only on the substrate, but also onto all of the hot chamber and support member components. Because the adhesion of the deposited material to the chamber and the support member is poor, the material tends to flake off over time creating particles within the system that can damage the chamber, the substrates, and the product. As a result, the deposited material must be removed periodically to avoid particle generation and contamination of substrates. The removal of the material is typically accomplished utilizing a low power fluorine containing plasma. In the case of tungsten, NF
3
is typically the cleaning gas of choice. The fluorine radicals of the low power NF
3
plasma attack the deposited tungsten during cleaning. However, the fluorine radicals also react with the aluminum of the support member to create an aluminum fluoride layer on the heater surface. Typically, this layer of aluminum fluoride is only about 0.0004 to about 0.0006 inches in thickness and does not create any detrimental effects as long as the thickness of the material is uniform. However, the grooves
14
,
16
shown in
FIG. 1
generally have a rectangular cross sectional shape which forms square comers at the intersection of the grooves
14
,
16
. Empirical studies have shown that the aluminum fluoride has greater accumulation at the intersections of the grooves of support members. This added accumulation of aluminum fluoride creates “pillars,” or raised areas, of aluminum fluoride which may exceed 0.004 inches. The pillars prevent the substrate from fully contacting the upper surface of the support member and interfere with chucking of the substrate by causing backside pressure failure. Accordingly, the pillars cause local heat transfer anomalies affecting film uniformity. Additionally, the NF
3
cleaning gas is drawn into contact with the substrate backside and into the vacuum channels which result in contamination of the substrate and chamber components.
One attempt to mitigate or eliminate the detrimental effects of build-up on the substrate support surface is disclosed in co-pending Application No. 08/893,858, entitled “Improved Substrate Support Member” which is incorporated herein by reference in its entirety. A “sculptured” upper surface of a substrate support member is shown having recessed areas for maintaining a vacuum condition therein. The recessed areas are defined by gradually sloping surfaces formed on the upper surface of the support member and extending from a raised portion to a depressed portion thereof. The sloping surfaces are tapered at the transitions between the raised portions and the depressed portions to eliminate sharp comers. Protrusions having rounded surfaces are disposed in the recesses and cooperate to provide a support surface for substrates. The vacuum condition is established by coupling the recessed areas to a vacuum supply via holes formed in the support member and terminating at the recessed areas. Thus, the problems associated with cleaning gases are overcome by eliminating intersecting grooves and by rounding the comers of the protrusions.
However, while the prior art support members achieved good deposition uniformity for 200 mm substrates, larger substrate sizes

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