Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Reexamination Certificate
1999-12-08
2003-04-08
Le, N. (Department: 2858)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
Reexamination Certificate
active
06545500
ABSTRACT:
BACKGROUND
1. Field of the Invention
This invention relates to the use of temperature change in determining the location and character of conducting point defects in or on flat-panel displays such as, but not limited to, those as used in laptop computers.
2. References
The following documents are incorporated by reference herein:
U.S. Pat. Nos. 5,804,980; 4,819,038; 5,334,540; 5,365,034; 5,430,305; 5,465,052; 5,615,039; 5,170,127; 5,831,392; 5,859,502.
PCT Publication Nos. WO99/36935; WO98/02899; WO99/06844; WO98/19501.
William C. O'Mara, “Liquid Crystal Flat Panel Displays Manufacturing Science & Technology” (1993).
Richard M. Bozorth, “Ferromagnetism”, IEEE Press, Copyright 1951 D. Van Nostrand Company, Inc.
Neil Ashcroft and N. David Mermin, Solid State Physics, Copyright 1976, Holt, Rinehart, and Winston.
Alexander Fetter and John Dirk Walecka, Theoretical Mechanics of Particles and Continua, McGraw Hill, Copyright 1980.
Robert M. Gray and Lee D. Davisson, Random Processes, Prentice Hall, 1986.
3
. Description of Related Art
A wide variety of electronic circuits are formed as a collection of interconnections between electrical or electronic elements. On any structure which is predominantly planar, locally or globally, it is often necessary for these interconnections to overlap each other. In some cases, the overlaps can be electronic components themselves, as in capacitors, diodes, etc. During the fabrication or operation of the device, it is possible that at the overlapping points or points of near contact unintended conductive or non-conductive paths can be formed. The presence of these paths can prevent the device from operating properly. From a manufacturing or repair point of view, it is a very difficult matter to identify the location of these unintended paths. Various techniques have been employed such as direct optical examination of the surface and electrical test using contact probes and electro-optical techniques (See, for example Henley U.S. Pat. No. 5,465,052). It can be very difficult or impossible to make direct contact near a potential defect, so usually external connections are used which may make it impossible to identify the exact location of the defect. In many cases, the defect does not have an optical signature of any form on the device. On the other hand, if it were possible to identify the location of these unintended paths, many different methods exist for their repair in situ. Therefore the rapid identification of the defect locations is highly desirable.
In the case of flat-panel displays, there is typically a regular array or grid of rows and columns on the display. As used herein, a flat-panel display is a visual information display device for which the dimensions of the active display plane are much greater than the thickness in a direction perpendicular to the display plane. Examples of such devices include liquid crystal displays(LCD) and field emission displays(FED). To fabricate the array on a flat panel display, there must be many, many crossover points over a large area. Therefore, the opportunity for defects to arise is very high. It is now a common practice in the liquid-crystal display manufacturing business to find and repair defects before final assembly of the display. Unfortunately, no entirely satisfactory means of locating these defects has yet been employed.
In the case of liquid-crystal displays (LCD), there is usually a regular array of interconnections and electronics which is capable of producing an electric field. Adjacent to this array there is a molecular substance which has the property of affecting optical polarization and/or transmission in relation to the applied electric field. With an appropriate collection of optical filters, glass, and electronics, this arrangement can be used essentially as a switchable “light-valve” which then leads to its utility as a flat-panel display.
In the case of a field-emission display (FED), there is typically a regular array of electron-emitting devices and light emitting devices situated opposite each other. Associated with this regular array is an array of interconnections and possibly electronics which resembles that of the LCD. By applying carefully selected voltages to the rows and columns of this structure, electrons may be emitted and strike the light emitting devices thereby leading to its utility as a flat-panel display. In the case of FED displays, the invention applies to the part of the display known as the cathode from which the electrons emanate into a vacuum region.
In the case of other types of flat-panel displays, regardless of the exact nature of the light switching or generation mechanism, there is typically also a regular array of interconnections and electronics. Appropriate voltages or currents are applied to affect the optical properties of the device which then leads to utility as a flat-panel display.
In all of the above described flat panel display devices, there is a need for rapid localization of defect points during or immediately after manufacture without making repeated or microscopic contact with the device. It is desirable that this localization can be performed both during and after the fabrication of the device. It is desirable that the localization not require an optical signature of the defect and that the method be reducible to an algorithm that a computerized machine can perform without operator intervention. It is desirable that the method would allow for repair of the device on the same machine on which the localization takes place.
Because of the very large size of modern flat-panel displays, the test machines built for this purpose tend to be very large and expensive. They must operate at a very high reliability level and with an extremely high level of cleanliness. Clean room space is also very expensive in and of itself. Often, if an operator is required for the operation, especially a repair operation, the operator is stationed on a different machine entirely and the devices under test are transported from the test machine to the machine with the operator entailing great logistical and material handling costs as well as creating cleanliness problems. It may be that the required cleanliness makes a special enclosed mini-environment for the tool a necessity or practicality. Within this mini-environment, the air is typically continuously filtered and other cleanliness measures are often employed.
Most modern flat-panel manufacturing operations are actively involved in process development as well. Therefore, it would represent a significant advance if it were possible to implement a test operation on a relatively small and inexpensive apparatus even if not applicable for volume manufacturing so as to facilitate failure analysis operations on the devices under manufacture.
The present invention can be implemented with hardware much simpler and less expensive than that of most test equipment used for similar purposes. The hardware required can be made extremely reliable and may have a minimum of moving parts. The overall throughput which can be achieved is extremely high. It is possible to build simple versions of the apparatus for failure Be analysis very economically. No contact to the active area of the flat-panel display is required. The present invention also allows for localization of defective points to exceedingly high resolutions without the need for operator guidance. In light of all this, it will be appreciated that the present invention constitutes of substantial improvement over prior art.
SUMMARY OF THE INVENTION
The present invention furnishes a group of analytical techniques and systems in which localized change in temperature is employed in determining the location and nature of defects in flat-panel devices. The nature of the defects includes the electrical properties, resistance or capacitance.
In the field of semiconductor integrated circuit manufacturing, techniques exist which are often referred to as OBIC (Optical Beam Induced Current) or LIVA (Light Induced Voltage Alteration). Several apparatus have been built for
Le N.
Nguyen Vincent Q.
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