Electrical connectors – Interrelated connectors relatively movable during use – Movement about axis
Reexamination Certificate
2000-01-20
2001-11-13
Picardat, Kevin M. (Department: 2822)
Electrical connectors
Interrelated connectors relatively movable during use
Movement about axis
C438S014000, C438S017000
Reexamination Certificate
active
06315574
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the testing of semiconductor wafers during manufacturing and specifically to the real-time in-line testing of semiconductor wafers during integrated circuit-fabrication.
BACKGROUND OF THE INVENTION
There are numerous individual operations, or processing steps, performed, in a strictly followed sequence, on the silicon wafer in the course of manufacturing a complex integrated circuit (IC). Each such operation must be precisely controlled in order to assure that the entire fabrication process yields integrated circuits displaying the required electrical characteristics.
Frequently, failure of an individual operation is detected only after the completion of the entire, very expensive, process of IC fabrication. Due to the very high cost of advanced IC fabrication processes, such failures result in the severe financial losses to the integrated circuit manufacturer. Therefore detection of errors in the manufacturing process, immediately after their occurrence, could prevent the unnecessary continuation of the fabrication of devices which are destined to malfunction, and hence, could substantially reduce the financial losses resulting from such errors.
Process monitoring in semiconductor device manufacturing relies upon the examination of the changes which occur in certain physical and/or chemical properties of the silicon wafer upon which the semiconductor devices are fabricated. These changes may occur following the various processing steps to which the silicon wafer is subjected and are reflected by changes in the electrical properties of the wafer. Therefore, by monitoring selected electrical properties of the silicon wafer in the course of IC fabrication, an effective control over the manufacturing process can be accomplished.
Not all of the electrical characteristics of a completed integrated circuit can be predicted based on the measurements performed on a partially processed wafer. Most of the characteristics however, can be predicted directly or indirectly based on the investigation of the condition of the surface of the silicon wafer (substrate) in the course of IC manufacture. The condition of the silicon surface is very sensitive to the outcome of the individual processing steps which are applied during IC manufacturing, and hence, the measurement of the electrical properties of the substrate surface can be an effective tool by which the monitoring of the outcome of the individual processing steps can be accomplished.
The determination of the electrical characteristics of the wafer surface typically requires physical contact with the wafer surface, or the placement of a contactless probe over a stationary wafer. In the latter case an optical signal or a high electric field is used to disturb equilibrium distribution of the electrons in the surface and near-surface region of semiconductor. Typically, the degree of departure from equilibrium is driven by variations of one or more electrical characteristics of the surface region, the near-surface region, and the bulk of the semiconductor. To obtain a more complete picture of the entire surface of the wafer, several measurements at various points on the surface can be made. Such a procedure, known as “mapping”, moves the measuring probe with respect to the measured material (or vice versa) over the surface of specimen, stopping at a number of locations and performing a measurement at each location before moving to the next location. The substrate, in this procedure, does not remain in the continuous motion, so consequently the applicability of such a method for use in real-time in-line process monitoring is limited.
SUMMARY OF THE INVENTION
The invention relates to an apparatus and method for the real-time, in-line monitoring of semiconductor wafer processing. In one embodiment the apparatus includes a probe assembly located within a semiconductor wafer processing line. As each wafer is carried beneath or above the probe assembly by conveyor belt, robotic arm, wafer chuck, or other similar device, a source of modulated light, such as an LED, within the probe assembly, generates light having a predetermined wavelength and frequency of modulation which then impinges upon the wafer. A sensor in the probe assembly measures the surface photovoltage induced by the modulated light. The signal from the sensor is sent to a computer which then uses the induced surface photovoltage to determine various electrical characteristics of the wafer, such as surface charge and surface doping concentration, among others.
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“Surface Charge Profiler” brochure mail
Kamieniecki Emil
Ruzyllo Jerzy
Picardat Kevin M.
QC Solutions, Inc.
Testa Hurwitz & Thibeault LLP
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