Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2000-09-26
2001-09-18
Zarabian, Amir (Department: 2824)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S679000, C438S686000
Reexamination Certificate
active
06291347
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates generally to the field of circuit fabrication and more specifically to a method and system for constructing semiconductor devices.
BACKGROUND OF THE INVENTION
The construction of semiconductor devices involves using controlled vapors to apply very thin metal coatings to silicon wafers. Chemical vapor deposition (CVD) is a process for applying these coatings. In this process, a volatile metal-organic precursor gas comes in contact with areas of a wafer where a metal film is needed. A chemical reaction occurs, resulting in the deposition of metal on the surface. The coatings, however, must be applied only to specific parts of the wafer. If the coating is deposited on the bevel or edge of the wafer, it may cause the coating on the frontside of the wafer to peel away. If the coating attaches to the backside of the wafer, it may contaminate other pieces of equipment as the wafer undergoes further processing. Finally, the precursor gas may reach areas of the equipment under the backside of the wafer, causing contamination of the process equipment.
Known methods for preventing a precursor gas from reaching the back parts of a wafer, or from contaminating the equipment include contact-based methods and purge-based methods. The contact-based methods use a ring to shield the bevel, edge, and backside of the wafer. The ring comes in contact with the front surface of the wafer in order to prevent the reactive gas from reaching the lower parts of the wafer. The contact methods, however, are problematic because contact with the wafer may cause particle generation. Moreover, the ring covers part of the wafer, reducing the area on which a coating may be deposited. In addition, since the ring is cooler than the wafer, it cools part of the wafer surface, causing a drop in the deposition rate, which leads to irregularities in the coating. In the purge-based methods, a ring partially shields the lower parts of the wafer without touching the wafer, leaving a gap between the ring and the wafer. An air flow of an inert gas is directed from under the shield through the gap to prevent the precursor gas from reaching the lower parts of the wafer. A problem with the purge methods is that the gas flow needed to prevent the precursor gas from entering the gap causes deformities in the metal coating.
While these devices and methods have provided improvements over prior approaches, the challenges in the field of circuit fabrication has continued to increase with demands for more and better techniques having greater effectiveness. Therefore, a need has arisen for a new method and system for constructing semiconductor devices.
SUMMARY OF THE INVENTION
In accordance with the present invention, a method and system for constructing semiconductors are provided that substantially eliminate or reduce disadvantages and problems associated with previously developed systems and methods.
According to one embodiment of the present invention, a system for constructing semiconductor devices is disclosed. The system comprises a wafer having semiconductor devices, a bevel, an edge, a frontside, and a backside. The system also comprises a chamber. A heater is coupled to the interior of the chamber and is operable to hold and heat the wafer. A showerhead is also coupled to the interior of the chamber and is operable to introduce a precursor gas containing copper over the frontside of the wafer. A shield is coupled to the interior of the chamber and is operable to partially shield the bevel, the edge, and the backside of the wafer from the precursor gas. The chamber has on opening through which a reactive backside gas may be introduced below the backside of the wafer.
According to one embodiment of the present invention, a method for constructing semiconductor devices is also disclosed. Step one calls for placing a wafer on a heater in a chamber. Step two requires heating the wafer with the heater. Step three provides for partially shielding the wafer with a shield. In step four, the method provides for introducing a precursor gas containing copper into the chamber above the frontside of the wafer. The last step calls for introducing a reactive backside gas into the chamber below the backside of the wafer.
A technical advantage of the present invention is that the shield does not come into contact with the wafer, thus avoiding the particle generation and coating irregularities associated with the contact-based methods, while allowing for more coating coverage than in the contact-based methods. Another technical advantage of the present invention is that the gas flow of the backside gas is sufficiently low to prevent the deformation of the coating that occurs with inert gas purge-based methods.
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Konecni Anthony J.
Russell Noel M.
Brady W. James
Mosby April M.
Smith Bradley
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
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