Apparatus and method for contact-free potential measurements of an electronic composition
AssigneeSiemens Aktiengesellschaft
InventorHans P. Feuerbaum
Life of this patent
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Abstract
A method and apparatus for the contact-free potential measurement at an electronic component using an electron beam wherein a predetermined potential is applied to the measuring point and the output voltage of a controlled gain amplifier is set to a predetermined reference value U.sub.S by means of controlling a photomultiplier voltage U.sub.PM and the photomultiplier voltage U.sub.PM is maintained constant. The measuring voltage U.sub.M is then determined from the difference of the voltages U.sub.R -U.sub.S between the control unit output voltage U.sub.R and the index value voltage U.sub.S. The method and apparatus allow the quantitative potential measurement to be made on the conducting paths of an integrated circuit without utilizing manual adjustments.
Claims7
A method for contact-free potential measurement of an electronic component with an electron microscope by means of measuring the energy of the secondary electrons with a spectrometer having a compensating circuit with a controlled-gain amplifier and to which a photomultiplier is connected, comprising the steps of connecting the measuring point of the component (12) to a pre-determined potential;
- and setting the output voltage (U.sub.R1) of the controlled-gain amplifier (38) to a pre-determined index value (U.sub.S) with the control of the photomultiplier voltage (U.sub.PM);
- and holding the photomultiplier voltage (U.sub.PM) constant and, subsequently applying an operating voltage to the component (12) and determining the measured voltage (U.sub.m) from the difference (U.sub.R -U.sub.S) between the control unit output voltage (U.sub.R) and the index value (U.sub.S).
Apparatus for contact-free measurement of an electronic component with an electron microscope and measuring the energy of secondary electrons with a scintillator comprising, means for connecting a pre-determined potential to said component (12);
- a controlled gain amplifier (38) connected to the photomultiplier (32) of said scintillator (26), a differential amplifier (46) connected to said amplifier (38) and its output supplies the measuring voltage (U.sub.m), a comparator (50) which can be switched to receive an input from said amplifier (38) and has a second input comprising an index value voltage (U.sub.S) and the output of said comparator (50) connected to control the photomultiplier voltage (U.sub.PM) of the photomultiplier (32) through a control device (56).
Apparatus for contact-free potential measurements of a test sample comprising, an electron microscope mounted to irridate said test sample with an electron beam to produce secondary electron emission, a voltage control unit, a first switch connected to said test sample to connect it to said control voltage unit or a first reference fixed potential, a scintillator mounted to receive said secondary electron emission, a retarding field electrode mounted between said test sample and said scintillator, a photomultiplier tube connected to said scintillator, a controlled-gain amplifier connected to said photomultiplier tube and supplying an input to said retarding field electrode, a differential amplifier receiving the output of said controlled-gain amplifier, a second switch connected to said controlled gain amplifier, a comparator connected to said second switch, a second reference potential connected to said differential amplifier and to said comparator, and the output of said comparator connected to control said photomultiplier tube.
Dependencies are inferred from the claim text.