Cleaning and liquid contact with solids – Processes – Including application of electrical radiant or wave energy...
Reexamination Certificate
1999-03-09
2001-07-03
Gulakowski, Randy (Department: 1746)
Cleaning and liquid contact with solids
Processes
Including application of electrical radiant or wave energy...
C134S001300, C438S905000, C156S345420
Reexamination Certificate
active
06254689
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention disclosed herein relates generally to a system and method of cleaning the chambers of semiconductor processing tools. More particularly, the present invention relates to a system and method of cleaning photoresist contamination in a semiconductor processing tool chamber by flash photolysis.
Hundreds of processing steps, known to those skilled in the art, are typically required to fabricate integrated circuits on semiconductor substrates. The integrated circuits are created from multiple layers of various materials, semiconductors, oxides and metals, and are collectively referred to as a wafer. The oxide and metallic layers are patterned using photoresist masks and etching to form the integrated circuit devices.
A photoresist mask is placed onto an oxide or metallic layer and then etching is used to selectively remove portions of the layer to create the desired pattern to form the integrated circuit device. After etching, the remaining photoresist is then removed or stripped from the surface of the wafer. Etching and stripping can either be performed in the same processing chamber or in separate chambers of a processing tool. During etching and stripping, photoresist contamination deposits on the surfaces inside the processing chamber. As additional semiconductors are processed, the photoresist accumulates and this buildup on the surfaces inside the chamber is the source of particulate photoresist contaminants which are damaging to the semiconductor devices processed in the chamber. Particulate contamination has the potential to degrade the performance and reliability of the integrated circuit devices. It has become increasingly more important to prevent harmful particulate contamination as integrated circuit devices have become increasingly smaller and correspondingly more sensitive to such contamination.
To prevent this damaging particulate contamination, etching and stripping processing chambers must be cleaned periodically to remove the photoresist deposits on the inside surfaces of the chamber before the deposits begin flaking and peeling and the particulate contamination inside the chamber reaches levels that are harmful to the integrated circuit devices being processed in the chamber. Typically, processing chamber cleaning is done “off-line” and the chambers are unavailable for production use during cleaning, thus, reducing the throughput of the processing tool. There is, therefore, a need to reduce the frequency of chamber cleaning and to delay cleaning until just prior to the particulate contamination becoming damaging to the integrated circuit devices being processed.
Conventional cleaning processes to remove photoresist from the surfaces inside semiconductor processing chambers include wet cleaning and plasma cleaning. During wet cleaning, the processing chamber is disassembled and its components are cleaned by hand in water or a solvent. Accordingly, wet cleaning is both labor intensive and time consuming. Plasma cleaning techniques are less labor intensive as they use either ion bombardment or a chemical reaction to remove the deposited contamination from the inside chamber surfaces. To avoid pitting or damaging the surfaces of the chamber, typically a chemically reactive plasma is used. The plasma is selected to react with and etch the deposit while minimizing the etching of the material comprising the surfaces of the chamber, which are typically aluminum. Other semiconductor processing chamber cleaning techniques include heating the surfaces of the chamber under low pressure and using special liners or coatings. These liners and coatings act as barriers to intercept the photoresist from depositing on the chamber surfaces or as thermal control coatings to reduce the amount of the deposits or to assist in the removal process.
It is recognized that during photoresist etching and stripping, photoresist contamination deposits and accumulates on the inside surfaces of the processing chambers, which must be cleaned regularly to avoid particulate contaminants damaging the integrated circuit devices being processed in the chambers. Although various cleaning techniques are currently available in the prior art, there is a need for a cost effective, easily implemented process for cleaning the photoresist contamination from semiconductor processing chambers.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a system and method of flash photolysis cleaning of semiconductor processing chambers, that combines the use of chemical reactions with heating of the photoresist to volatilize the photoresist contamination.
It is another object of the present invention to provide a system and method of cleaning semiconductor processing chambers that uses ultraviolet (UV) radiation to concurrently generate the reactive agent and to preferentially heat the photoresist by utilizing the absorption properties of photoresist.
It is another object of the present invention to provide a system and method of cleaning semiconductor processing chambers that are cost effective and easily implemented in existing semiconductor processing tools using readily available materials.
It is another object of the present invention to make the fabrication of integrated circuit devices of increasingly smaller dimensions feasible by reducing photoresist particulate contamination in semiconductor processing chambers that can degrade performance and reliability of advanced integrated circuit devices.
It is another object of the present invention to provide a simple and less time consuming system and method of cleaning photoresist contamination in order to increase the throughput of the semiconductor processing tool by reducing chamber downtime.
It is yet another object of the present invention to provide a system and method of cleaning photoresist contamination from semiconductor processing chambers that can be used in conjunction with traditional cleaning techniques to reduce the frequency of cleaning by such traditional methods and thereby reduce downtime.
It is yet another object of the present invention to provide a system and method of cleaning semiconductor processing chambers that make it easy to determine when the chamber is sufficiently cleaned by using a detector to evaluate the gas flow exiting the chamber during cleaning.
The above and other objects are achieved by using flash photolysis to produce a chemical reaction in combination with preferential heating of the photoresist to volatilize the photoresist contamination on the inside surfaces of the semiconductor processing chamber. To provide a simple, efficient system and method of cleaning the processing chambers UV radiation both generates the reactive agent and preferentially heats the photoresist, thereby cleaning the photoresist contamination from the chamber.
UV radiation can be transmitted through a window into the processing chamber, or generated directly inside the chamber, and once inside, it is reflected by the metallic surfaces inside the chamber. However, photoresist is designed to absorb in the blue and the ultraviolet regions of the spectrum, so the photoresist deposits on the inside chamber surfaces will preferentially heat. By flowing oxygen into the chamber while exposing the chamber to UV radiation, the UV radiation will not only preferentially heat the photoresist, it will convert some of the oxygen into the highly reactive oxidizing agent ozone, which will react with the heated photoresist to convert it to volatile products that are carried by the gas flow out of the chamber. The volatilization of the photoresist produces low molecular weight volatile products such as water and carbon dioxide.
Some of the above and other objects of the present invention are also achieved by evaluating the gas flow out of chamber and thereby detecting when the cleaning process is sufficiently complete. The UV-rich discharge is generated using a UV emitter source, for example, a UV flashlamp such as a xenon photoflash lamp. The pulsed UV radiation is emitted into the chamber until
Chaudhry Saeed
Gulakowski Randy
Lucent Technologies - Inc.
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