Image analysis – Applications – Manufacturing or product inspection
Reexamination Certificate
1999-03-17
2001-06-26
Boudreau, Leo (Department: 2621)
Image analysis
Applications
Manufacturing or product inspection
C382S170000
Reexamination Certificate
active
06252981
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to die inspection systems, such as those used in the inspection of dies formed from semiconductor wafers, wherein the die inspection system selects dies that are formed from the wafer that are to be used to create a reference model for determining whether other dies that are formed from the wafer contain defects or flaws.
BACKGROUND
Semiconductor devices are typically manufactured from ingots of crystalline semiconductor materials that have been sliced into wafers having a predetermined thickness. These wafers are then cut into dies having predetermined dimensions, such as 0.5 cm. by 0.5 cm. The dies are then etched and oxidized using various chemicals and masks, such that predetermined circuits are created on the dies. Such processes are well known in the art.
During the manufacture of such devices, defects or flaws may be formed or inadvertently created on one or more dies before or after they have been cut from the wafer. Such defects or flaws will typically cause the device to misoperate. It is desirable to detect such defective or flawed dies before the dies are shipped to a customer. Although systems and methods have been implemented that may be used to detect defective or flawed dies, such systems and methods require an operator to set up each wafer, such as by selecting dies that are not defective that are then used to create a model. The model may then be compared with other dies of the wafer. The systems and methods then perform the comparison between the model die and each die of the silicon wafer, thus reducing the time required to check each die of the silicon wafer as compared with manual inspection of each die.
While such inspection systems have decreased the time and operator involvement that are required to inspect each die of a silicon wafer, operator setup of the inspection system now occupies a significant portion of the time required to inspect the dies. Accordingly, there has been a need for a system and method for detecting defective or flawed dies that does not require an operator to manually select model dies for each new wafer.
SUMMARY OF THE INVENTION
The present invention provides improved systems and methods for selecting multiple dies from one or more wafers of semiconducting material that have allowable levels of defects. These selected dies are then used to create a comparison reference to detect defective or flawed dies that have been formed on the wafer of semiconducting material.
In accordance with one aspect of the present invention, a system for selecting reference die images, such as for use with a visual die inspection system, is provided. The system includes a die image comparator, which compares a first die image to a second die image to create a difference image that contains only the differences between the two die images. The system also includes a difference image analysis system that receives data from the die image comparator. The difference image analysis system analyzes the difference image and determines whether there are any features of the difference image that indicate whether the first die image or the second die image should not be used as a reference die image.
In accordance with another aspect of the present invention, a system for inspecting dies is provided. The system includes a camera that is used to obtain images of one or more dies. A reference die detection system is connected to the camera. The reference die detection system determines whether a first die image and a second die image may be used as reference images.
Still further in accordance with the invention, there is provided a method for selecting a reference die image. The method includes subtracting a first die image from a second die image to create a difference image. For example, a numerical value associated with each picture element of the first die image may be subtracted from the numerical value associated with each corresponding picture element of the second die image in order to create the numerical value of each corresponding picture element of the difference image. It is then determined whether the difference image contains unacceptable data.
The die selection system of the present invention eliminates the need for an operator to manually view and select dies that will be used for comparison with other dies that have been formed on a wafer to determine whether such dies contain surface flaws or defects that are indicative of devices that will misoperate.
Those skilled in the art will further appreciate the advantages and superior features of the invention together with other important aspects thereof on reading the detailed description which follows in conjunction with the drawings.
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Guest Clyde Maxwell
Harris Charles Kenneth
Roy Rajiv
Akin Gump Strauss Hauer & Feld L.L.P.
Boudreau Leo
Rourk Christopher J.
Semiconductor Technologies & Instruments, Inc.
Werner Brian P.
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