Cleaning and liquid contact with solids – Processes – For metallic – siliceous – or calcareous basework – including...
Reexamination Certificate
2000-11-08
2003-09-16
Meeks, Timothy (Department: 1762)
Cleaning and liquid contact with solids
Processes
For metallic, siliceous, or calcareous basework, including...
C134S021000, C134S022100, C134S031000, C427S248100
Reexamination Certificate
active
06620256
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods and apparatus for removing accumulated material deposits, e.g., film deposits, from processing chambers, and more particularly, to non-plasma in-situ cleaning of interior surfaces of semiconductor processing chambers.
2. Description of the Related Art
In the processing of a semiconductor wafer, to form integrated circuit structures therein, it is desirable to deposit materials including, for example, tungsten (W), titanium (Ti), tantalum (Ta), polysilicon, and/or silicon nitride on the wafer by a chemical vapor deposition (CVD) process. Chemical vapor deposition may occur by a conventional thermal CVD process, which involves supplying reactive gases to a substrate surface where heat induced chemical reactions (homogenous and heterogeneous) take place to produce a desired film. In the alternative, a plasma process may be implemented wherein a controlled plasma is formed to decompose and/or energize reactive species to produce the desired film.
Whether utilizing the thermal or plasma CVD process, thin films of deposited materials accumulate in the interior of the CVD deposition chamber. As a result, these thin film deposits must be removed periodically because they tend to affect the reproducibility of thin film deposition processes by changing the dimensions of the chamber. Also, the thin film deposits can flake off and contaminate the wafer being processed in the chamber.
In the current state of the art, it is conventional to remove such deposits using several different cleaning methods, including wet cleaning and in-situ cleaning.
The wet cleaning method necessitates the need for breaking the processing chamber's vacuum seal and manually wiping down the chamber's interior surfaces. Strong acid solutions are often used to dissolve the deposits on the interior surface of the chamber. Upon completion of the cleaning process, the chamber must be reassembled and resealed.
Inherent problems associated with this approach include the high volumes of hazardous chemicals that must be used in the cleaning process. Additionally, the manual breakdown of the processing system and subsequent reassembly is labor-intensive, time-consuming, increases wear on the processing chamber components, and may leave residual contamination within the chamber.
An in situ cleaning process is performed without disassembly of the process chamber. Typically, either plasma is generated for a dry etching process or a gaseous agent is flowed through the process chamber to remove accumulated films.
A plasma-enhanced cleaning process operates by introducing a continuous stream of gaseous fluorinated molecules, such as CF
4
, NF
3
, C
2
F
6
, C
3
F
8
, SF
6
into a vacuum deposition chamber. A plasma is then ignited in the chamber during the gas flow, by connecting to a high frequency (radio or microwave) field. The increased energy creates atomic fluorine which promotes a reaction between the cleaning gas and any residue accumulated on the interior surfaces of the processing chamber.
While this process satisfactorily removes residues, the plasma physics require the continuous flow of large quantities of highly fluorinated gaseous molecules to maintain the plasma. In turn this generates highly reactive atomic radicals in the presence of the high frequency field. These reactive radicals lead to excessive amounts of extremely reactive and hazardous air pollutants, such as F
2
and HF. Additionally, these plasma reactions are often only 40% efficient in the destruction of any perfluorinated compounds (PFC) gases that may form which are known to have a global warming potential (GWP) at least three times more powerful than CO
2
, and a lifetime of several thousands years in the atmosphere.
Another in situ method to remove residues from process chambers involves the introduction of a continuous flow of voluminous amounts of hazardous materials, such as HF or interhalogens, which also pose a significant risk to humans and the environment.
U.S. Pat. No. 4,498,953 describes an in-situ cleaning method in which an interhalogen, such as BrF
5
, BrF
3
, CIF
3
, or IF
5
is continuously flowed through the processing chamber while maintaining a predetermined pressure within the chamber. At the end of the treatment, the flow of the interhalogen gas is terminated. However, a significant amount of hazardous material is moved through the system. Clearly, the high volume of material utilized in this method not only increases the cost of production but presents ancillary costs relating to the disposal of hazardous materials.
A similar problem exists in the process disclosed in U.S. Pat. No. 5,565,038 wherein a continuous flow of an interhalogen gas is introduced into a processing chamber to be used as a cleaning agent. Again, the flow of reactive gas is ongoing, and not terminated until the film removal is completed. Still further, as in the prior art cited above, this method is inherently problematic because of the large quantities of hazardous materials that are utilized, and the associated costs to the manufacturer and/or the environment. Additionally, the continuous flow cleaning process is performed under very low pressure and cleaning efficiency is reduced under such condition.
Other known methods for removing deposit buildup in processing chambers utilize NF
3
, including the types used in thermal CVD processes such as, vertical tubes. However, very high temperatures are required to crack NF
3
, to release the reactive fluorine ions. If these temperatures are not reached and/or maintained, hazardous NF
3
is exhausted to the surrounding environment. In addition, the poor reaction selectivity of fluorine ions results in unwanted etching of the quartz reactor. Still further, depending on the shape of the processing chamber, uniform cleaning is not always predictable or accomplished.
Accordingly, it would be desirable to provide an improved cleaning process for deposit removal in a processing chamber, without the disadvantages of generating highly reactive radicals that may subsequently form perfluorinated greenhouse gases and/or using voluminous quantities of hazardous material thereby increasing production costs, disposal costs, and exposure risks to personnel.
SUMMARY OF THE INVENTION
It is a principal object of the present invention to provide an improved non-plasma cleaning method for removing deposits in a chemical vapor deposition chamber, utilized in either a plasma or thermal process, that reduces the volume of etching gas used in the cleaning method.
Another object of the present invention is to provide an improved non-plasma cleaning method that introduces a sufficient amount of an etching gas into a chemical vapor deposition chamber to effectively remove deposits therein with reduced production costs.
Still another object of the present invention is to provide an improved non-plasma cleaning method that does not generate unnecessary amounts of hazardous waste materials.
Yet another object of the present invention is to provide an improved non-plasma cleaning method that operates at higher pressures thereby increasing speed of the reaction rate.
A further object of the present invention is to provide an improved non-plasma cleaning method that operates at higher temperature thereby increasing the efficiency of the cleaning agent.
A still further object of the present invention is to provide an improved non-plasma cleaning method that uses reduced volumes of etching material but with increased utilization rates.
In one aspect, the present invention relates to a method for removing solid residue from interior surfaces of a processing chamber, by introducing a reactive substance into the interior of the processing chamber. The pressure is adjusted in the processing chamber to a predetermined level. When the pressure is adjusted, the introduction of the reactive substance into the processing chamber is terminated or substantially discontinued. The reactive substance is retained in the processing chamber for a sufficient
Arno Jose
Tom Glenn M.
Wang Luping
Advanced Technology & Materials Inc.
Chappuis Margaret
Fuierer Marianne
Meeks Timothy
LandOfFree
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