Temperature control of a substrate

#This invention relates to an improved method of controlling the temperature of a substrate clamped to a substrate support in a deposition chamber.

#As semiconductor substrates become larger, and devices formed therein become smaller, new materials and processes must be developed for making these devices. For example, the use of aluminum, which has long been used to make conductive paths and contacts, is being supplanted by copper, which is more conductive and thus has a lower resistivity. Further, copper has superior electromigration properties than does aluminum, even, for example, aluminum doped with silicon. Thus copper has some superior properties for integrated circuits.

#A problem with using larger substrates, e.g., silicon wafers, is that processing uniformities are more difficult to maintain across the larger wafer; processing must be uniform across the diameter of the wafer in order to produce devices that are the same across the wafer, irrespective of their position on the wafer. As 8 inch diameter wafers are replaced with wafers of approximately 12 inches in diameter (200 mm diameter), this is not a trivial task.

#FIG. 1 is a schematic cross sectional view of an ionized metal plasma chamber suitable for use in the invention.

#FIGS. 2A and 2B are photomicrographs of a deposited copper seed layer taken at the center (2A) and periphery (2B) of a substrate deposited in accordance with a prior art process.

#FIGS. 3A and 3B are photomicrographs of a deposited copper seed layer deposited in accordance with the process of the invention.

#A minimum pressure of the temperature control gas must be maintained between the substrate support and the clamped substrate in order to sputter deposit a thin (seed) uniform metal layer across the diameter of a substrate.

#FIGS. 2A and 2B illustrate the difference in morphology of a copper seed layer on a silicon substrate. Near the center of the substrate, the seed layer is smooth and uniform; but near the edge of the substrate the seed layer is rough and non-uniform.

#FIG. 2 illustrates a seed layer of copper deposited on the sidewalls of an opening in a silicon substrate in accordance with the method of the prior art. The substrate was clamped to the support and an argon gas was passed to the backside of the substrate so that the gas had a pressure of about 10 torr behind the substrate during deposition of a copper seed layer. The photomicrograph of FIG. 2A was taken at the center of the substrate, and it is apparent that the seed layer is fairly smooth. However, the photomicrograph of FIG. 2B was taken at the edge of the substrate, and it is apparent that the copper seed layer has a rough, uneven surface.