Radiant energy – Ionic separation or analysis – Methods
Reexamination Certificate
2001-04-18
2004-04-27
Lee, John R. (Department: 2881)
Radiant energy
Ionic separation or analysis
Methods
C250S281000, C438S745000, C436S043000, C436S047000, C436S052000, C134S002000, C134S010000, C134S022140, C134S032000, C134S048000, C134S071000, C134S079000, C134S080000
Reexamination Certificate
active
06727494
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to a method and an apparatus for detecting contaminating species on a semiconductor wafer and more particularly relates to a method and apparatus for detecting metal particles on a wafer edge by exposing the wafer edge to an acid solution and then analyzing the acid solution.
BACKGROUND OF THE INVENTION
In the fabrication of semiconductor devices, one of the most important aspects of increasing yield of a fabrication process is to reduce defect density, defined as the number of defects per square centimeter of wafer surface area. The defects on the surface of a wafer found during wafer processing are attribute by various forms of contamination. For instance, particle contamination including those of metal particles or non-metallic ions amounts to more than 80% of all defects. The detection of such contamination on a wafer surface becomes even more important as device technology goes down to the sub-micron range, i.e. 0.25 &mgr;m or below. The ability to detect wafer contamination is therefore of utmost importance to the fabrication of semiconductor devices.
In recent development in fabrication technology, the scaling down of devices to dimensions suitable for sub-half micron technology has a serious effect on manufacturing yield and reliability of the integrated circuits produced. The processing complexity increases with each generation of chips, partially caused by the need for additional mask layers to form interconnects for the increased number of sub-circuits designed on the chip. This makes the IC devices more susceptible to contamination introduced by particulate, ions and chemical impurities occurred at each processing step. Moreover, smaller devices produced are more vulnerable to smaller defects and smaller amounts of chemical impurities that may result in unacceptable chip quality. The cleanliness of a wafer surface during processing, or the amount of contaminants on the wafer surface, must be closely monitored to ensure the quality of the IC devices fabricated.
In order to monitor the amount of contaminants of trace organic or inorganic impurities on a wafer surface, such as Cl
−
, F
−
and SO
4
−−
, etc, a wafer surface must be pretreated by rinsing or immersing in ultra-pure water or other suitable solvent to dislodge the contaminants. A sample of the ultra-pure water containing the impurities is then analyzed by ion chromatography, gas chromatography or mass spectrometer analysis. Conventionally, a sample is obtained on a wafer by dripping a solvent on the wafer surface directly while the wafer is exposed to ambient air which may itself contain contaminants. Results achieved by the conventional method of analysis is poor and the accuracy of contaminant determination is grossly inadequate due to additional deposition of particulate contaminants on the wafer surface during sample collection. Moreover, when devices such as micro-pipette is used to transport sample solution from a wafer surface to a sample collection bottle, incomplete or inadequate transfer further results in quantitative determination error. There has not been any reliable method proposed in the industry for collecting contaminant samples from a wafer edge.
Metal particle contaminations of a semiconductor wafer surface can seriously deteriorate electrical characteristics of the semiconductor devices formed. For instance, a deterioration may be caused in the breakdown voltage of a gate oxide or in the P—N junction leakage current. Metal particles such as Fe, Cu, Co, Na and other metal particles which are contaminating sources may be produced by the chemicals used in the previous fabrication process or may be produced by the fabricating equipment. Presently, the only method available for detecting the contaminating of wafer by metal particles is limited to a detection on the top surface of the wafer. There is no reliable method for detecting any contamination occurring at the wafer edge which frequently happens after a copper sputtering process and a backside cleaning process. For instance, Co is frequently used in forming contacts on a wafer, while Cu is frequently used in forming via interconnect on the wafer surface. A cross-contamination of the two different metal particles during subsequent processes can cause serious defects in semiconductor devices fabricated. The capability for detecting contamination on a wafer edge therefore becomes an important requirement for insuring the reliability of a fabrication process that involves metal deposition.
It is therefore an object of the present invention to provide a method for detecting contaminating species on a wafer edge that does not have the drawbacks or shortcomings of the conventional methods.
It is another object of the present invention to provide a method for detecting metal particles on a wafer edge that cannot be detected by the conventional detection methods.
It is a further object of the present invention to provide a method for detecting contaminating metal particles on a wafer edge by providing a solvent container for exposing the wafer edge to a solvent.
It is another further object of the present invention to provide a method for detecting contaminating metal particles on a wafer edge by exposing the wafer edge to a diluted HF solution for removing metal particles and then analyzing the solution.
It is still another object of the present invention to provide a method for detecting contaminating metal particles on a wafer edge by first mounting the wafer to a support structure and then exposing the wafer edge to a diluted acid solution for removing metal particles from the wafer edge.
It is yet another object of the present invention to provide an apparatus for collecting contaminating species from a wafer edge that is less than 10 mm from the outer periphery of the wafer.
It is still another further object of the present invention to provide an apparatus for collecting contaminating metal particles from a wafer edge that includes a container for holding a volume of a solvent and a wafer mounting device for supporting a wafer over the container with only a predetermined edge portion of the wafer exposed to the solvent.
It is yet another further object of the present invention to provide an apparatus for collecting contaminating metal particles from a wafer edge by utilizing a solvent container that has an arcuate bottom formed with a radius between about 10 cm and about 15 cm for holding either a 200 mm diameter wafer or a 300 mm diameter wafer.
SUMMARY OF THE INVENTION
In accordance with the present invention, a method and an apparatus for detecting contaminating species on a wafer edge are provided.
In a preferred embodiment, a method for detecting contaminating species on a wafer edge can be carried out by the steps of providing a wafer that has contaminating species on an edge portion, providing a container that has a cavity therein for holding a volume of a solvent, exposing the edge portion of the wafer to the volume of solvent, and analyzing the volume of solvent and determining the contaminating species.
The method for detecting contaminating species on a wafer edge may further include the steps of providing a rotatable shaft that has a first end that is free and a second end that is attached to a bearing mounted in a support structure, the support structure has an adjustable height, mounting the wafer at a center point to the first free end of the rotatable shaft, positioning the wafer vertically in the container and adjusting a height of the bearing such that only a predetermined edge portion of the wafer is exposed to the volume of solvent and rotating the wafer with the edge portion contacting the volume of solvent by turning the rotatable shaft. The method may further include a step of filling the container with a volume of solvent that includes an acid, or filling the container with a volume of solvent that includes HF, or filling the container with a volume of solvent that includes HF in water at less than 20 volume percent concentrat
Lee John R.
Souw Bernard
Taiwan Semiconductor Manufacturing Co. Ltd.
Tung & Associates
LandOfFree
Method and apparatus for detecting contaminating species on... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for detecting contaminating species on..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for detecting contaminating species on... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3248435